Abstract: The existing methods for suppressing the strength of interference signals in the networks can suppress interference signals effectively but they cause a limit to the transmission capacity of the networks at the same time. To solve this problem, a method of setting guard zone in wireless Ad-hoc network is proposed to suppress interference and the optimum radius of guard zone is derived. Theoretical analysis and simulation results show that the proposed method could greatly reduce the level of interference signal and reasonable radius of guard zone could increase the transmission capacity. The transmission capacity will reach maximum due to an optimum radius of guard zone.