Abstract: Credit discrimination is a common phenomenon in our economy，and it would affects the economy in different ways．For the purpose of analysis the macroeconomic impacts of credit discrimination， a dynamic stochastic general equilibrium model is considered with firm’s default risk and bank’s credit screening behavior, and the macroeconomic effects of monetary policy with banks’ credit screening are investigated. On the basis of parameters calibration, the dynamic path of macroeconomic variables after monetary policy shocks hit the economy is simulated, that is，the impulse response functions of monetary policy．They shows that，firstly，bank’s credit screening restrained the positive effects of monetary policy both for the long and short term，that is to say，the positive effects of positive monetary policy shocks would be smaller when bank’s credit screening existed．Secondly，further，the short term effects of monetary policy shows that bank’s credit screening restrained the real effects of positive monetary policy shocks，and augmented its effects on inflation．That is，when there is bank’s credit screening behavior，the impacts of positive monetary policy on output，employment，investment，and the other real variables will be smaller than the bank’s credit screening behavior disappeared．But when there is bank’s credit screening behavior，inflation will arise much higher when positive monetary policy proposed．Last but not the least important，when comparing the impulse response functions of positive and negative monetary policy shocks, it is found that bank’s credit screening leads to a asymmetric effects of monetary policy．Further，the result of welfare analysis argues that，compared with the circumstance without bank’s credit screening，bank’s credit screening makes the aggregate welfare deteriorates．The results implies that，the monetary policy authority should pay more attention to the asymmetric effects of monetary policy for the purpose of scientific decision of monetary policy．

Key words: default risk; credit screening; monetary policy; asymmetric effects