The litter decomposition and influence factors in Calamagrostis angustifolia wetland in Sanjiang Plain are studied using mesh bags. As time passed, the weight reduction rate is increasing and the decomposition rate is decreasing. The decomposition is faster when the litter in 0~10 cm, and slower when in the deeper. Using correlation analysis and primary components,the temperature-humidity condition and pH are the major environment factors which could affect the litter decomposition of Calamagrostis angustifolia wetland. The Olson's single exponent model was adopted to simulate the dynamic of the litter decomposition rate and the remnant rate.