The work aims to improve microhardness of Al-17.5Si-0.3Nd alloy surface by modifying the surface with high current pulsed electron beam (HCPEB). Changes in surface morphology and performance of HCPEB-modified alloy were studied with FESEM, EPMA, XRD, and Vickers hardness tester. SEM and EPMA analysis results revealed that Al substrate and microcrack-free halo structure were generated on the surface of HCPEB-treated alloy, and all elements on the alloy surface were distributed uniformly in modified layer. XRD analysis results showed that no new phase was formed after HCPEB treatment, and all diffraction peaks broadened and shifted. Diffraction peaks firstly moved toward high angle and then toward low angle as pulse numbers increased. The largest shift angle was present in the sample treated with 5 pulses. In addition, microhardness test results demonstrated that microhardness of Al substrate increased from 534.95 MPa (for initial sample) to 1258.59 MPa (sample treated with 25 pulses) as pulse number increased, while microhardness of the halo microstructure sharply decreased from 10067.7 MPa (for initial sample) to 1390.29 MPa (sample treated with 25 pulses) as pulse number increased. The grains of alloy surface are markedly refined after HCPEB modification, and surface hardness of alloy surface is increased as a whole.