Tl-2212 bicrystal Josephson junctions on SrTiO3 substrates have been fabricated. The I-V characteristic of a Josephson junction under microwave radiation were measured，and microwave induced steps were observed in accordance with the Josephson frequency-voltage relationship. The RCSJ model including noise of bicrystal Josephson junction was constructed through numerical simulation，and the results of simulation were in good agreement with the experimental data. Using the RCSJ model，we investigated the effect of noise on the dynamic characteristics of Josephson junction through simulation，and explained the phenomenon of reduced height and increased breadth of the minima of microwave induced steps. We proposed that the effective noise temperature should be the sum of operational temperature and equivalent temperature of the external noise.