A novel bi-directional micro-strip antenna fed by coplanar wave-guide (CPW) is proposed to obtain circular polarization (CP) radiation. Two square patches, fed by coupling through the CPW open stub, are selected as the radiating elements. Perturbation segments are added at different sides of the square patches. Same rotation CP radiations in two opposite directions are achieved by adding perturbation segments. The symmetrical characteristics of the antenna suppress the even mode in the CPW line. Measured results show that the proposed antenna has a -10dB return loss bandwidth of 11.6% and a CP bandwidth of 1.86%. Left-hand circular polarization (LHCP) appears on both sides of the antenna. The theoretical results accord with the measured results well.