Corrosion behavior of TP316L was investigated with simulated atmosphere and ash deposition for the superheater in biomass boiler. Corrosion dynamic curves were plotted by mass gain. The results showed that the corrosion was dependent on temperature and was greatly accelerated by ash deposition. The mass gain was distinctly reduced in the presence of SO2 with and without ash deposition on the specimens. Corrosion rates with ash deposit at different temperatures were calculated. Two feasible methods were provided to avoid serious high-temperature corrosion in the biomass boiler.