Abstract: To improve precision of the signal conditioning circuit in an automatic test system, an error compensation approach was proposed based on the Loose Type of Wavelet Neural Network (L-WNN), combining wavelet transform with BP neural network. It was applied to get the error curve which stands for the relationship of input voltage and the error of conditioning circuit. To evaluate the performance of the L-WNN model, the error curve was also compared to it got by BP neural network and regression analysis which applied Least Squares Estimate (LSE). The effect of testing on the compensation result shows that significant improvements can be made and that is an efficient method to compensate the error of the signal conditioning circuit.