A temperature-dependent neutron cross-section library for MCNP in in-hospital neutron irradiator mark 1 reactor was generated using NJOY software. Accounting for the temperature range for reactor operation, a compact ENDF (ACE) data library was created. The accuracy of the self-making library was validated by comparing data with MCNP/4B standard library and the results were tested by ICSBEP (International Criticality Safety Benchmark Evaluation Project) benchmark problems, which was used in the calculation of Doppler temperature coefficient. Influence of different parameters in the processing was also analyzed. The results showed that the ACE format library produced in this paper was correct and could be used reliably for physics design at IHNI-1 reactor.