A current-based temperature sensor chip was designed and implemented. The influence of temperature measurement principle and Early effect on temperature measurement accuracy was analyzed, and a collector-emitter voltage compensation circuit was proposed. The transfer function between the output current and the temperature was linearized by using a set of current mirrors and matched resistors. By this way, the chip’s measurement linearity and accuracy were improved. A reverse bias protection circuit was designed to increase the reverse voltage that the chip can withstand. The chip was designed and fabricated in a 40 V complementary bipolar process. The measurement results show that the nonlinear error of the chip is ±02 ℃, and the temperature measurement accuracy is less than ±03 ℃in the temperature range of -55～150 ℃.