By lightly doping in a-Si: H films in the process of low-temperature annealing, the density of the nualeation centers was controlled, and the films of larger grain polysilicon with good quality were obtained. The results show that the crystallization was almost uniformly proceed in(， and direction (slightly faster in direction), the average grain size is about 1μm, the mobility is about 92 cm２/V·s, and the dark conductivity at room-temperature is between 10-２s/cm and 10-4s/cm. The optical gaps of the crystallized films were determined between 1.16-1.22eV from the absorption spectrum. The coefficient of optical absorption within the wave length range of 800-1000nm is on the order of 104cm-1, and the absorption efficiency is around 60%.The results of heavily doped annealing samples of a-Si:H, as a contrast, are also discussed.