The manuscript tried to estimate the impacts of BVOC emissions on ozone and SOA during 1981-2018 using modelling method. The topic long term variation of background ozone and SOA is interesting, but there are still some problems need to be further clarified in this manuscript.

1. Model evaluation should be added. The authors should show evidences to make the results convincing, especially the BVOC emissions.
2. The manuscript focusedon the change of background ozone and SOA in China due to the change of vegetation The MS should show the change of biomass as well as how the biomass changes affecting BVOC emissions.
3. The history simulation setting is not reasonable by fixing the meteorology in 2008 (as listed in Table 1). Why 2008 was chosen in this study? The BVOC emissions are very sensitive to meteorology change, and the meteorology is an important factor influencing the emission and air quality. Fixing the meteorologymay induce the unreasonable results which should be discussed in the MS. Many factors influencing the BVOC emissions and their atmospheric chemistry in the past 4 decades. A method should be set to clarify the multivariate effects.    
4. The logic is weak, and the text need to bere-organized. Each section in the results seems loose respectively, and the main line of the manuscript has not been highlighted. The topic is long term impacts variation, I think carry out the discussion in chronological order will be better. What’s more, that disturbs the readers’ thinking by posting the figure of spatial variations in BVOC emissions in Jun 2018 and explaining the emission situation in section 2.1.
5. Overall the explanations are lack of mature andthe scientific thinking is not

Also, I have some suggestions for the authors to revise the manuscript:

• Section 2.2:  Using a table to list the model settings is better to list them in a paragraph
• Table 2: Don’t branch the percentages of BVOC contribution
• The form of picture display should be strengthened

Overall, this paper has the potential to be a useful contribution to the body of literature after major revisions. My concerns are:

Section 2.1: I recommend that you show a spatial map of changes in BVOCs over time? Li et al. (2020) shows only 2008-2018.

In the introduction your say that your study uses “more accurate BVOC emissions”. However, you don’t provide evidence of this. Satellite data of formaldehyde could help in the evaluation over the satellite era. Do a literature search as there are a number of studies that use HCHO data to constrain BVOC emissions. How will you validate your emissions before the satellite era (e.g., 1981-2004)?

Table 1: Why do you use “Year 2008” for your “HISTORY” run, but “Year 2018” for the rest of your simulations?

Line 176: Can you show a map of the simulated VOC to NOx ratio to help you make your point. Also, there are a number of papers discussing the VOC to NOx ratio over China, including as observed from space. For example: Jin, X., T. A. Holloway (2015). Spatial and temporal variability of ozone sensitivity over China observed from the Ozone Monitoring Instrument. Journal of Geophysical Research Atmospheres , 120(14), 7229–7246, doi: 10.1002/2015JD023250. Please do a literature search to see what they’ve concluded and if those conclusions are consistent with your study.

It would also be helpful to show a spatial map of the simulated NOx distributions.

Line 192: Can you mark (with boxes, for instance) the 5 regions on one of the maps, such as Figure 2?

Line 245: “N3”? Do you mean NO3?

Line 275: You don’t show the BVOCs emission changes for your study in “HISTORY”. Why? A spatial map of the changes would be very helpful for the discussion.

Section 3.3.1: The discussion would be facilitated by maps (e.g., in supplementary material) of vegetation changes, leaf biomass changes, emission factors, etc.