The corrosion behavior of Mg-6Zn, Mg-6Zn-1Ca and Mg-6Zn-1Mn alloys in Phosphate Buffer Saline (PBS) solution were studied by XRD, SEM, EDS, 3D profilometer and weight loss method, and the corrosion mechanism of the three alloys were discussed. The results show that the addition of Ca and Mn can reduce the weight loss rate of the alloy, but the weight loss rate of the alloy with Mn addition (W_r=3.91 % after immersed for 10 days) is lower than that of the alloy with Ca addition (W_r=6.78 %), indicating that Mn element has better corrosion resistance to PBS, which is related to the formation of dense oxide film on the surface of the alloy with Mn addition. At the same time, Mg-6Zn-1Mn alloy shows that pitting corrosion is caused by the primary battery composed of the second phase and the matrix. After solution treatment at 420 °C for different holding time (2~20 h), the corrosion pit of the alloy surface decreases with the increase of holding time, indicating that long time solution treatment can reduce the galvanic corrosion between the second phase and the magnesium matrix, and increase the tendency of uniform corrosion of the alloy.