<p>Medical waste (MW) is characterized by rapid growth and considerable variability in generation volume, which poses substantial challenges for its treatment. Co-incineration with municipal solid waste (MSW) provides an effective emergency disposal strategy that maximizes the utilization of existing incineration capacity. In this study, numerical simulations were conducted to systematically investigate the combustion behavior of MW co-incinerated with MSW in a large-scale MSW incinerator and simultaneously took into account the influence of bed height on combustion characteristics. The effects of varying MW blending ratios on combustion characteristics were analyzed, and the air distribution parameters were further optimized. The results indicate that a 5% blending ratio of MW represents a suitable upper limit beyond which excessive temperature rise and pollutant emissions may occur. Under this condition, a primary air fraction of 69% and a flue gas recirculation (FGR) ratio between 15% and 16% yield optimal furnace performance, characterized by enhanced combustion uniformity and minimized NO_<i>x</i> emissions. These findings provide theoretical guidance and operational reference for the practical application of MW co-incineration in MSW grate furnaces.</p> Graphical abstract <p></p>