Synthetic aperture focusing technique (SAFT) has the advantage of high resolution, can be used in near-field and the ability of three-dimensional image formation. The focusing precision of the beamformer is the key factor that influencing the synthetic aperture imaging quality. A digital synthetic aperture beamformer is presented used in pipeline girth weld inspection, and the key points of FPGA implementation are also introduced. The testing results illustrate that this beamformer has good ultrasound formation ability, high lateral resolution and good performance.