In the field of sensor, especially distributed fiber sensor, the primary signal has the characteristics of weakness and periodicity. After passing through the receiving circuit, the signal is distorted unavoidable and the following signal processing will be influenced greatly. On the basis of theory analysis of the receiving circuits of weak and periodic signals, a self-adaptive processing algorithm based on weak periodic signal is proposed. The algorithm is used to process receiving signals so that the distortion of output signals is reduced greatly. A common processing method for optimizing and compensating output signals is realized.