Abstract: Based on the multi-channel thermal model and the power model, the calculation code which could be used in the transient safety analysis of fast reactor was developed in unprotected overpower accident, unprotected loss of flow accident and unprotected loss of hot sink accident in the paper. By this code, the core reactivity, power and thermal parameter changes with time in different accident cases were calculated and the core neutronics and thermal-hydraulics performance was analyzed. The results indicate that the core design has safety features when accident happens.