During the short-term horizon, thermal dynamics have significant effects on the reliability of the integrated electricity-heat systems (IEHS). In this paper, the short-term reliability of IEHSs is analyzed considering thermal dynamics. Firstly, the contingency management model for IEHSs is established based on the integrated electricity-heat optimal power flow technique. Both the node method and first-order equivalent thermal parameters model are incorporated to represent thermal dynamics of pipelines and buildings respectively. Then, the framework for the short-term reliability evaluation of IEHSs is proposed by combining the contingency management model and time-sequential Monte Carlo simulation techniques, as well as several novel reliability indices. The proposed techniques are validated using an integrated electricity-heat testing system.