In this paper, a multi-mode signal generation system based on high speed ECL digital circuits is introduced. The method to design LFM and NLFM signal systems is also discussed. The implemented system working at clock frequency of 280MHz can output LFM and NLFM signals with different time duration and frequency bands within 70MHz. The measurement results of the system show that its performances of harmonic and spurious signals less than-55dB. It can meet the needs of practical engineering applications.