Abstract: The objective of this study was to determine the effects of mowing time and interval on dry matter(DM) yield and chemical composition of Leymus chinensis based on L.chinensis Meadow in Songnen Plain.The results showed that as the mowing time delayed, L.chinensis DM yield increased quadratically with peak DM yield of 255 g·m^-2 on August 15^th (P=0.002).Mowing time affected crude protein (CP) yield quadratically with two peak values which were 12.3 g·m^-2 on June 15^th and 14.2 g·m^-2 on August 1^st, respectively, but there was no significant difference.The CP content of L.chinensis decreased lineally (P<0.001) and its neutral detergent fiber (NDF) and acid detergent fiber (ADF) increased linearly (P<0.001) as the mowing time extended.The fist cut of mowing in spring season was extremely important.In present study, DM Yield and CP yield of L.chinensis on June 1^st was significantly (P<0.05) higher than May 15^th and CP yield of L.chinensis on June 1^st had no significant difference compared with other mowing time except for August 1^st.So, the optimal mowing time was June 1^st.Different mowing interval affected the DM yield and chemical composition (except for ash) of L.chinensis significantly (P<0.05).When the mowing interval was 50 d, L.chinensis DM yield and CP yield was significantly (P<0.05) lower than 30 and 40 d mowing interval, and NDF and ADF contents in L.chinensis were significantly (P<0.05) higher than 30 and 40 d mowing interval.When the mowing interval was 40 d, L.chinensis DM yield and CP yield was higher than 30 d mowing interval but had no significant difference.Besides, as the mowing interval increased, the CP (P<0.001), phosphorus (P=0.001) and potassium (P< 0.001) contents in L.chinensis decreased linearly.In conclusion, based on DM yield and CP content, the optimal mowing regime for L.chinensis grasslands was: initial mowing June 1^st and mowing interval 40 d.