Abstract: A formula of positive temperature coefficient of resistance (PTCR) of conductive rubber filled by carbon black (CB) used for temperature sensor was given by general effective media theory. The sensitive coefficient was analyzed by the equation of sensitive coefficient deduced from the formula of PTCR and the impact of the strain and resistivity on PTCR effect. The formula of PTCR is constant in the experiment when the CB is homogeneously dispersed and the volume fraction of CB is close to the critical threshold. A dilution of the volume fraction of CB due to the volume expansion of the composites has a significant influence on PTCR effect. When the volume fraction of CB is within the percolation zone, the sensitive coefficient is from 280 to 420, and it is from 32.5 to 62.0 when the volume fraction of CB is within the conductive zone. PTCR effect is a complex process of the heat-deformation and the deformation-conductivity. Due to the low coefficient of cubical expansion, the conductive carbon black/rubber has high sensitive coefficient, but the value of PTCR is low.