The present invention discloses a sperm selecting system and the method thereof. The brief concept of the present invention is to generate a flow field by hydraulic pressure difference then utilize the property that the sperm swims against the flow field so as to difference the sperms by vitality thereof. One of the main features of the present invention is that the sperms be selected are initially set at the entrance of the flow field instead of the exit of the system. Furthermore, an activating design can be selectively added to the present invention so as to activate the sperm be affected by the process of freeze storing.