Abstract: A case study on the observation of the prefrontal stratiform cloud precipitation Sichuan in spring was made based on an aircraft measurement with PMS FSSP-100, OAP-2DP and others. It is found that the precipitation from the stratiform cloud was not always stimulated by the natural seeding from high level cirrus. It may be created by the aggregated ice crystals in form needle, sheaths, columus and graupels from riming in stratiform cloud itself, especially in the convective clouds complexes embeded within the stratiform cloud system. The mass growth of those rain embryos is mainly occurred in the negative temperature layer. For a graupel embryo with initial diameter D=600μm, the mass growth in negative temperature layer hold 70% or more of total mass growth.