Log-ratio processor working at 500 MHz applied to turn-by-turn beam position measurement was implemented. The processor circuit consists of two logarithmic amplifiers and a subtraction circuit. The output value is proportional to beam position. Before, the upper usable frequency of logarithmic amplify is lower than 500 MHz. At present, several manufacturers support higher upper usable frequency of logarithmic amplifiers. In this paper, we present the performance test result of the 500 MHz log-ratio processor applied to turn-by-turn BPM electronics.