In this paper, we successfully fabricate polycrystalline silicon films with very large and uniform-size grains by the method of nanometer thick aluminum induced crystallization (nano-AIC) on the a-Si:H film deposited by plasma enhanced chemical vapor deposition (PECVD). The effect of annealing ramp-up time is discussed. Four different annealing ramp-up time, 1,5,10,20 hours, are tested. The results show the maximum average grain size obtained in this paper is about 60 μm under the condition of 20-hour annealing ramp-up time. The nano-AIC specimens show a much better leakage current characteristics than the AIC specimens since the Al layer in AIC process is much thicker and was not removed completely from the polycrystalline silicon film during Al wet selective etching process.