Intensity changes of convective cells in the Hangzhou Bay observed by Zhoushan radar from January 2007 to June 2010 when entering the sea are studied, and they depend on the combined reflectivity factor, ET, VIL, radial velocity, hail index and so on. The results show that the possibility of convective cell strengthening or its maintenance nearby the coastline is quite big. Meantime, the possibility of convective cell strengthening nearby the north coastline is big, while the possibility of convective cell weakening nearby the south coastline is also big. The possibility of convective cell strengthening or maintaining from evening to dawn is still big. The temperature and humidity characteristics in the coastline， the surface wind convergence， and atmospheric stability are analyzed from three typical cases. And the mean values of the temperature, relative humidity gradients and horizontal wind shears in the Hangzhou Bay concerning various cell changes are calculated. The result shows that the three factors above of the strengthening cells are bigger than the weakening cells. In conclusion, the above three conditions should be considered when judging a convective cell in the Hangzhou Bay is strengthening or weakening.