Purpose <p>This study conducted an in-depth investigation on the forward radiation field characteristics of a multi-beam X-ray source. The study revealed distribution characteristics at different distances, beam number, spacing, and tube voltage.</p> Methods <p>Based on multi-beam X-ray source with 45 linearly arranged focal spots, the dose field distribution was analyzed through Monte Carlo simulations and validated by measurement data. A radiation measurement platform was established, and measurement data verified the accuracy of the Monte Carlo simulation results.</p> Results <p>The research results show that under an anode voltage of 160 kV and an anode current of 15 mA, the forward radiation field of the 45 focal spot multi-beam X-ray source decreases from 62.2 mGy/s at the center to 22.3 mGy/s at the edges at a distance of 20 cm from the focal spot distribution line, and to 6 mGy/s at 80 cm forward distance. Unlike the peaked radiation pattern of a single-beam X-ray tube, this configuration exhibits a gentle-slope distribution and an end truncation effect, referred to as a quasi-line-source characteristic. Further simulations demonstrated that the near-field region in front of the focal spot distribution line shows an alternating peak–valley pattern, which disappears in the far-field. For a 160 kV multi-beam X-ray source, the positions of these peaks and valleys correspond closely to the focal spot spacing and shift closer as the tube voltage increases.</p> Conclusion <p>The findings of this work provide useful references for the radiation field characterization, imaging dose evaluation, physical system design, and shielding design of multi-beam X-ray imaging systems.</p>