On the basis of the structure of a pole conductivity detector for an integrated low voltage electrophoresis chip,a contactless conductivity detecting circuit is designed according to the working principle of high frequency contactless conductivity detecting,which consists of an AC inspiriting signal generator,a I-V convertor,a multiplicator,a low-pass filter and a differential amplifier.By using less devices and simple structures to realize powerful detecting,the circuit resolves the problem difficult to detect the very weak signals of low voltage electrophoresis chips. Finally,a test is applied to a electrophoresis chip to detect the contactless conductance signals of different concentrations of K+ by using the detecting circuit with an AC inspiriting signal of 10 V and the inspiriting frequencies of 450 kHz and 1 MHz.The experimental results show that the circuit can distinguish the lowest concentration of 10-9,and can reach the high linearity and resolution power in the ranges of 10-9-10-5.For its detecting functions,this circuit is able to used in other conductivity detecting fields.