RF circuit board has a significant impact on performance of the Digital Beam Position Monitor (DBPM) in storage ring of a synchrotron radiation facility. In this paper, a front-end RF board is designed for DBPM, and schematics of the RF board and the test results are given. In view of the inevitable inconsistency in the multi-channel circuit, a calibration circuit is designed to reduce such an influence. The test results show that the calibration method is useful for beam current dependence which is sensitive to channels inconsistency.