With higher standard of the new semiconductor processes and materials, the advanced package technology is developed rapidly.The concept and development of SIP(system in package) are described,its advantages are stated,its wide applications are illuminated.It is pointed out that SIP is the integrating result of knowledge,technique and process in IC industry.SIP can furthest optimize the system property,avoid the repeat of package,shorten the design period,cut the cost and raise integration.Mastering SIP is the key for entering the mainstream of package field,and the development prospects are great.