Due to the low effective sampling points, low data signal-to-noise ratio (SNR), and lower measurement resolution in the current single-pass digital Beam Position Monitor (BPM), a digital BPM measurement improvement algorithm for “beam single-pass” case is proposed. This algorithm enhances the effective sampling points by employing the “power division-delay-synthesis” technique for the analog signal. It improves the SNR of the sampling data through various data processing techniques, including data truncation, data concatenation, and digital bandpass filtering (BPF). Consequently, the resolution of the BPM is significantly enhanced. Experimental results demonstrate that this algorithm improves the measurement accuracy of the single-pass BPM by approximately two times without increasing the Analog-to-Digital Converter (ADC) sampling rate. The measurement method studied in this paper presents a novel solution for enhancing the measurement resolution of the single-pass BPM and has been successfully implemented in the Beijing Electron Position Collider II(BEPCII) and High Energy Photon Source (HEPS) linear accelerator projects.