A comparative analysis is made of two severe convective weather events occurred over the Zhoushan islands in 2004 by means of the data from new generation Doppler weather radar. One has extreme rainfall, while the other has extreme gales. The reflectivity, radial velocity and other secondary radar products of the two cases are analyzed, and some similarities and differences are found out. Both cases have seen organized strong echoes, strong wind areas in radial velocity pictures, vertical wind shear, high echo tops, and large VIL (Vertical Integrated Liquid water). Heavy rainfall happened when the echoes moved slowly while strong gales happened when the echoes moved quickly. The case of extreme gales had higher echo top, greater reflectivity and VIL. The wind convergence, mesoscale cyclone and vertical wind shear at lower levels may produce heavy rainfall. The mesoscale cyclone and vertical wind shear at middle and upper levels may produce strong downburst or hails.