Abstract: The HELIOS program built-in multi-group library does not include all the nuclides in the accelerator driven subcritical system(ADS) when it is applied in ADS assembly calculation. To solve this problem, the generating HELIOS format multi-group library method applicable for ADS assembly transportation calculation is studied. Based on ENDF/B VII.0, following the flow scheme of multi-group library generation, a new 45 groups library is generated for ¹⁶O that included in HELLIOS program built-in multi-group library, and examined at micro and macro levels. The results indicate that the method of generating multi-group library is correct. For nuclides that are not in the built-in multi-group library, HELLIOS program built-in 112 groups library is expanded and numerically validated by ADS cell. The results further indicate that the method of generating multi-group library is correct. Since the results calculated by HELIOS have large deviation from that by MCNP, the method to improve a multi-group library is proposed and numerically validated. The results indicate the relative deviation is obviously reduced after improvement compared to the original one.