Abstract: A thermal-hydraulic microcomputer code SELTAC (secondary loop transient analysis code) for transient analysis for secondary loop of pool type sodium-cooled fast reactor (SFR) was developed using FORTRAN language. In the SELTAC, the model of IHX (intermediate heat exchanger), OTSG (once-through steam generator), SBT (sodium buffer tank), and pump was established. The code was verified by the shutdown transient test data of CEFR (China Experimental Fast Reactor). The results show that the calculated value is consistent with the test value, the maximum relative deviation is no more than 4.34%, and the coincidence degree is better. An emergency shutdown accident was analyzed for a 600 MW SFR based on the combined code between SELTAC and primary loop transient analysis code, when the main heat transfer system was normal. The thermal-hydraulic transient characteristics of the secondary loop provide a reference for the design of large commercial SFR.