A tri-band wearable antenna fed by coplanar waveguide (CWP) with an artificial magnetic conductor (AMC) reflector is presented in this paper. The radiation patch consists of three open inverted triangles for multiband, and the ground is defected for better impedance matching The AMC unit is composed of three concentric nested regular octagonal rings. And to improve the performance of gain, the unit achieves three reflection zero phases at 1.8, 2.45 and 3.5 GHz corresponding to the three bands of the antenna. The proposed antenna based on AMC has been fabricated and measured. The working frequency bands are 1.34–1.67 GHz, 2.33–2.47 GHz and 3.55–3.7 GHz. The measured gain has increased by 3.4, 1.8, 4 dBi at 1.8, 2.45 and 3.5 GHz, respectively. The scenario that the antenna is placed on the human arm is also considered and experimented for wearable applications. The results are in good agreement with the simulation data and verify that the antenna has good robustness. When the antenna is conformal with the human tissue, the specific absorption rate (SAR) is calculated and reduced by about 99.8% after adding AMC reflector. Hence the proposed antenna has excellent wearable safety and is compatible with LTE 1800, WLAN, WiMAX communication systems.