According to the requirement of "Instruction for Earthquake Situation Analysis at Site" (revised by Seismological Bureau of China), a system PTDSS (Post-Earthquake Tendency Decision Support System)was built which combined with data processing, earthquake locating, expert system and database as one system.In this system, FAM (Fussy Associative Memory)model is used to make this system having function of self-learning, the main characteristic of second generation expert system.In the knowledge base not only many experts' experiences are collected;but also many valuable new knowledge learnt by system itself is included which is meaningful for tendency decision making up and up to now it is still not summarized by prediction expert.The results of examination for earthquake cases show the system possesses good prediction ability.