The formation of ozone (O3) is a complex nonlinear process including several factors. The contribution of one factor consists of its pure contribution and synergistic interaction with other factors. The impacts due to anthropogenic volatile organic compounds (AVOCs) and biogenic volatile organic compounds (BVOCs) emissions on ozone concentrations are calculated by a numerical method named factor separation technique and the improved regional air quality model (RAQM). It is indicated that O3 formation depends significantly on the relative ratios of AVOCs to BVOCs. Most of the total contributions of AVOCs or BVOCs in the areas with elevated emissions of AVOCs or BVOCs are from synergistic contributions of AVOCs and NOx or BVOCs and NOx. BVOCs play a minor role in the surface O3 formation in most areas of East Asia except some areas with high emissions of BVOCs in spring. The total contribution of BVOCs has a remarkable daily variation and may be less than the synergistic contributions of BVOCs in some periods, depending on meteorological conditions and emissions. This suggests that O3 control measures from episodic studies may be not feasible in long-term (e.g., seasonal) O3 reductions. Anthropogenic emissions in the northern areas of China (north of 30°N) should be reduced whereas both anthropogenic and biological emissions in the southern areas with elevated emissions of BVOCs should be considered for O3 controls.