Thin films of Mn1.95Co0.77Ni0.28O4 with a thickness of 6.5 μm were prepared by the magnetron sputtering method annealed at temperatures of 400℃, 500℃, 600℃, 700℃, 800℃ respectively. The negative temperature coefficient of resistivity (NTCR) of the films at room temperature α295 increases firstly, and then decreases with the growing annealing temperature. However, the resistivity of the films at room temperature ρ295 keeps decreasing with the growing annealing temperature. The sample annealed at 500℃ has the minimal normalized noise spectral density (SV·VR/V2), while that annealed at 700℃ has the maximal. The annealing process produces defects in the films, which lower the thermal conductivity and augment response time τ as well as the detector noise.