Abstract: The aim of the study was to determine the optimum harvest time by analyzing nutrients in common cordgrass（Spartina anglica） harvested at different mowing time and to analyze its nutritional value.The results showed that the common cordgrass was in grass withering period from December to next March,and it began to turn green on April 8 and then entered tillering and jointing stage on April 28.The vegetative stage was from June to September.The common cordgrass began to ear on September 10.The initial bloom stage was September 26,and it entered the flowering stage in October or November.The seeds matured in November and came into the grass withering period in December.The optimum harvest time for the common cordgrass was June and September.The nutrient contents of common cordgrass harvested at the optimum time are as follows： crude protein,9.26%;calcium,1.10%;phosphorus,0.11%;NDF,54.29%;ADF,34.14%;Ash,7.93%;and NaCl,1.54%.The unit nutritional value of microbial silage of common cordgrass was 6.54 Yuan,which was more economical than that of alfalfa,oat,chinensis and other high-cost forages.