Thin films of Mn-Co-Ni-O (MCNO) with different cation ratios were deposited by the magnetron sputtering method. By analyzing the material structure, it can be found that the grain size grows gradually with increasing Co cation number with constant Mn cation number, while the lattice parameter grows first and then decreases. The preferential orientation of thin films changes from (311) plane to (400) plane with increasing Mn cation number and the properties of thin films are unstable when the Co cation number is constant. The electrical properties show that both of Mn cations and Co cations participate in the conductivity, and Mn1.2Co1.5Ni0.3O4 has the lowest resistivity (235 Ω·cm) as well as the highest negative temperature coefficient of resistance (NTCR) |α295| (47%·K-1) at room temperature.