Abstract: Single event transient(SET) propagation in logic chains is studied, and it is shown that the pulse width has a major impact on broadening or attenuation of SET. Using SET propagation model and soft error rate (SER) analysis model to validate SER, on the basis of the two models, the method of SER at the gate level for combinatorial logic is improved, evaluation method for SER in combinational circuits to radiation is developed. Electrical masking effect has a significant influence on SER, using transient propagation model concerned electrical masking effect.