A 28-day leaching-decomposition experiment was conducted to study the effects of microbial activity and leaching on the initial decomposition of Calamagrostis angustifolia litters taken from the boggy meadow and meadow in Sanjiang Plain of China. The results showed that the mass loss of the litters at their initial decomposition stage accounted for 59% and 22% of yearly mass loss, respectively, and the remaining dry mass decreased significantly after 28-day decomposition. By the end of the experiment, the N content in the litters decreased by 32.65% and 24.55% , and P content decreased by 36.71% and 45.15%, respectively. The N and P contents in the litters treated with chloroform were higher than those of the control, but the difference was not significant. No significant difference was also observed in the N and P release from the litters to the leachates between the treatment of chloroform and CK, which indicated that the initial decomposition of the litters was mainly affected by leaching. There was no significant difference in the decomposition rate and nutrient loss rate between the two litters.