Understand"His bark is worse than his bite."

It means that a person makes a great many threats but doesn't follow through on them.

Like a barking dog that sounds vicious, but does not actually bite.

thank you
As a chinese girl ,I'm much obliged to receive your reply after I posted my question.If I did'nt express my thanks in time,please forgive me . Because I'm a college student,and we just use the computers at a fixed time in the class.
Now best wishes!