To address the issue of substantial waste heat generated during proton exchange membrane fuel cell operation not being effectively recovered，a water-steam dual‑heat source plate heat exchanger was designed to improve energy utilization efficiency.By varying its inlet conditions，the effects of steam and coolant temperature changes on the thermal characteristics of the heat exchanger were systematically analyzed.The results show that as the steam temperature increases，the proportion of steam heat exchange can reach up to 40% of the total heat exchange.As the coolant temperature increases，the proportion of coolant heat exchange can reach up to 82% of the total heat exchange.During the experiments，the heat transfer coefficients on the steam side and the coolant side reached maximum values of 156.9，783.44 W/（m²⋅K），respectively，indicating that the coolant side plays a dominant role in the dual‑heat source plate heat exchanger.Furthermore，as the steam temperature increases，the heat exchange efficiency gradually decreases；as the coolant temperature increases，the heat exchange efficiency gradually increases.Among these，steam temperature has a more significant impact on heat exchange efficiency：for every average increase of 1 ℃ in steam temperature，the heat exchange efficiency decreases by approximately 0.74%.The findings provide a reference for multi‑heat source waste heat recovery.