Abstract: As a new conceptual reactor, traveling wave reactor (TWR) is under fundamental research phase. The physical and mathematical models of the main parts of the primary circuit of TP-1 sodium cooled TWR designed by TerrraPower Co. were established, and the transient and safety analysis code TAST for sodium cooled TWR was preliminarily developed with Fortran program. Steady state analysis proves that the stability and dependability of TAST code for TWR are preserved. The variations of main parameters for loss of flow and reactivity insertion accidents were calculates, the results show that TWR is safe under such two transients.