To meet the needs of real-time characteristics as well as to overcome the time overhead caused by memory copying operations during the process of semispace collection,an improved method was proposed which was based on partial copying mechanism.Based on the fact that the large objects are always long-lived objects as well as distributed continuously in memory space,the lived large objects will only be marked without being moved during the collection phase of semispcae GC.The marked objects remain in the original space,and a compaction phase is added to maintain a low degree of memory fragmentation.SPECjvm2008 and Dacapo test suites are used to demonstrate the effectiveness of the proposed algorithm.Comparison experiments shows that proposed method can efficiently reduce the average pause time of the collection and ensure the realtimeness for semispace garbage collection.