Abstract: According to the thermogravimetric curve diagram of porous nickel foam in air, different oxidation heat treatment temperatures were employed for high temperature treatment, and the effect of the oxidation heat treatment temperature on the microstructure and electromagnetic microwaves of porous nickel foam was studied by TG-DSC, XRD, SEM, and vector network analyzer to explore the possibility of the application of porous nickel foam in electromagnetic pollution environment. The results show that when the oxidation heat treatment temperature exceeds 600℃, the surface of the porous nickel foam skeleton has obvious changes. When the oxidation heat treatment is 900℃, the surface forms a flaky structure, and when the oxidation heat treatment temperature reaches 1200℃, the surface becomes molten. The phase analysis indicates that with the increase of the oxidation heat treatment, the nickel oxide is formed on the surface of the porous nickel foam network. The electromagnetic absorption performances in the X-band are tested, and the porous nickel foam obtained by the oxidation heat treatment at 900℃ owns the most excellent microwave absorption performance, the reflection loss of which reaches the minimum value of −19.66 dB at 10.88 GHz, indicating that a certain oxidation heat treatment could effectively improve the microwave absorbing properties of the porous nickel foam.