Experimental Advanced Superconducting Tokamak (EAST) is the fully superconducting Tokamak. The EAST magnet system comprises 16 D-shaped toroidal field coils and 14 poloidal field coils which are cooled by supercritical helium at 4.2 K and 3.8 K. The temperature of superconducting coils is measured by Cernox as a new type low-temperature sensor, and monitored during the cooling and operation. The helium temperature can offer reference for quench signal. In this paper, a technique for the weak temperature signal measurement of superconducting coils is introduced, and its weak voltage is extracted from the intrinsic noise of the amplifier by the low-noise instrumentation amplifier, filter circuit, and high-linearity analog optocoupler. The temperature detection circuit works accurately and safely whether in cooling or operating process. This technique is an effective for the temperature detection on the low-temperature superconducting coils.