Surface modifications of polyethylene (PE) by various microwave plasma (N-2, CO2, O-2) were investigated and compared. These plasma treatment all improve the hydrophilicity of samples and introduce oxygen-containing groups into the samples surface. Moreover amine was also formed for the N-2 plasma-modified. The effect of N-2 plasma modification is best on the improvement of surface hydrophilicity, and its modification depth is about 5 similar to 6 nm, which can be got by calculating from the result of angular dependent ESCA analysis. The influences of sample location, microwave power, system pressure and treatment time on hydrophilicity of plasma modified PE were also studied. The results show that a similar pattern and the optimal operation conditions are suited for these plasma treatment.