A possible reason for the unreasonable simulation of maximum rainfall location, intensity and seasonal evolution over eastern China in CCM3 has been investigated. The analyses focus on the relationship between the simulated East Asian subtropical westerly jet biases and the seasonal evolution of rainbelt over eastern China. Comparisons of the simulated and observed precipitation distributions indicate that the simulated maximum rainfall location, intensity and seasonal evolution are inconsistent with reality. The simulated westerly jet center is located to the north of 40(N, which shifts eastward and northward and strengthens, compared with NCEP/NCAR reanalysis. The correlation analysis shows that there exists a significant positive correlation between the maximum rainfall amount and zonal wind at 200 hPa over the Great Bend of the Huanghe River. Thus the simulated unrealistic heavy precipitation in the inland area of western China is related to the biases in the location and intensity of the East Asian subtropical westerly jet. Further analysis indicates that the temperature differences from south to north in the lower troposphere and the larger sensible heating over the southeast Tibetan Plateau are responsible for the westerly jet location and intensity biases. Therefore, much more attention should be paid to the accurate simulation of the surface heating near the Tibetan Plateau and the location and intensity of the East Asian subtropical westerly jet for the improvement of precipitation simulation over East Asia.