Slip casting and pressureless sintering were used to produce NiFe₂O₄ ceramic U-shaped protection sleeves for thermocouple in aluminum electrolysis. The stability of slurry, sintering behavior of green body as well as the temperature measuring performances, were investigated in detail. The Zeta potential of slurry was improved effectively by adding 10wt% NiFe₂O₄ nanopowders and 5wt% nano-binder, and the slurry possessed better sedimentation stability when pH was in the range from 10.0 to 11.0. Green bodies began to shrink significantly when the sintering temperature rising to 1100 ℃. The linear shrinkage and linear shrinkage ratio increased with temperature, and the linear shrinkage ratio reached its maximum at 1300 ℃. The sintering activation energy of the initial stage was 295.11 kJ·mol ^-1, and the main transport mechanisms were volume diffusion and grain boundary diffusion. The temperature testing results showed that the assembled thermocouple with NiFe₂O₄ ceramic protection sleeves worked well with timely response to temperature variation, as well as good resistance to thermal shock and corrosion from melt salts, with the prospect of industrial temperature measurement applications in an aluminum reduction cell.