Abstract: The CDAS realtime telemetry and attitude determination system of meteorological satellite FY2 is a system of multifunction long life time and high reliability ,based on multiprocessor concurrent processing and multilevel faulttolerant architecture.It implements integrally realtime processing of analog telemetry including demodulation of accurate sun pulse,realtime determination of satellite's attitude,coding telemetry demodulation and realtime data processing,satelliteground loop simulation test,and processing of mass data,graphics and characters,communication and recording in realtime,etc.