Abstract: In designing multi-clock scan test,the cross of signals from one clock domain to another will increase the number of test patterns and cost of testing.In order to improve the design-for-test the cross signals in different clock domains are blocked using multiplexers at scan test mode.Clocks belonging to different capture groups are placed in the same group,so the number of test patterns and cost of testing are reduced. Meanwhile,the fault coverage can be maintained almost the same.Experiments prove that the method described is efficient and can be easily implemented at RTL level.