A series of Mn 1.5−x Co 1.5 Ni x O 4 (0≤x≤1.2) negative temperature coefficient materials was synthesized by the sol–gel method. The optimal pH of reaction solutions was obtained by theoretical calculation. XRD and X-ray intensity ratios (I 220 /I 440 ) and (I 440 /I 422 ) studies showed that as-sintered ceramics are single spinel structures with different cation distributions. The Ni 2+ ions not only enter B-site but also occupy A-site. Electrical studies showed that with increasing Ni content, the resistivity decreased from 909.229Ωcm to 221.873Ωcm initially in the range of x≤0.5 and then increased to 726.933Ωcm when x=1.2, whereas the B value decreased from 4427K to 2134K. In addition, different sintering temperature ceramics were investigated. A higher sintering temperature results in lower resistivity and B value at same Ni content. The Mn 1.0 Co 1.5 Ni 0.5 O 4 material showed much improved electrical stability at 125°C for 1000h. The rate of change (ΔR/R) is 0.2%.