The absolute position and intensity are fundamental parameters for the synchrotron radiation beamline. An double-wire X-ray Beam Position Monitor (XBPM) was manufactured to solve the problems in BSRF-3B3 diagnosis. We stated the significance of developing a double-wire XBPM and introduced the optical principle, physics design, mechanical design, data collection and operating effect in detail. At BSRF-3B3 beamline, an XBPM system was developed for the absolute position and intensity detection. The information obtained from the XBPM system is guidance for adjusting the B orbit parameters, and measuring vertical position and Full Width at Half Maximum (FWHM). The XBPM system plays an important role in the performance optimization of BSRF-3B3 beamline.