The invention relates to an internal combustion steam engine that is based on the internal combustion thermodynamic generator. The variable radiators are taken out from the traditional engine, while the warm keep cover, and heat absorbing water spray system formed by water tank, low pressure water pump, water cooling heat exchanger, high pressure pump, high water sprayer, are installed on the outside of traditional engine and connected through the water delivery pipe according to the above order, thereof, the high pressure water sprayer if installed on the high temperature part of the firebox; besides, by reforming the fuel atomization and spraying device onto the air-changing channel to make engine save energy and the more environment-protective.