This paper conducted a very comprehensive investigation of the model simulation of VOC using the Community Multiscale Air Quality (CMAQ) model and compared it with an excellent observation dataset including 28 sites across China. On one hand, they showed an overall underestimation of the VOC concentration, these biases often occurred in industrial cities. On the other hand, this VOC model simulation bias may lead to lower O3 predictions in China. The gap between VOC model simulation and observation may also influence the diagnosis of ozone production sensitivity regimes and other air pollution problems like the atmospheric oxidation capacity and the secondary aerosol formations. Therefore, I believe this topic is fundamental and critical to the atmospheric science community. This paper is well-written, and the data analysis convinced me. I would like to recommend this paper be published in ACP subject to add more detailed information about the VOC measurement as well as some minor corrections.

1. In the method Section, although the author cited the literature to support the introduction of VOC measurement. However, I strongly recommend that the authors add a more detailed description of measurement techniques and uncertainties, as this part may also greatly affect the comparison of observations and simulations. Considering that there are currently large differences in the consistency between models and observations in different regions, the authors need to clarify further whether VOC observations in all sites have adopted uniform sample-analysis and data quality control standards, in other words, whether these systematic differences may be due to uncertainties in VOC measurements?
2. I suggest the author further highlight the problem of overprediction of HCHO since it is very important for ozone formation. Although the VOC is underpredicted, the modeled high HCHO may narrow the real gap between the simulated and observed ozone.
3. Figure 2 NME and NMB should give the full name.
4. Figure 4-6 missed the caption, making it hard for the readers to follow the paper.
5. Figure 3 y-axis ppbv change to concentration (ppbv).
6. Table S1. “Sites in the PRD belong to Urban” change to “Sites in the PRD except GZ belong to Urban”

The specific comments have been included in the attachment.