The invention provides a device for simulating the explosion of combustible cloud and steam cloud in confined spaces. According to the device, a size-variable collapsible frame is designed; combustible gas cloud explosion process model experiments in confined spaces of different structures can be carried out; a liquid atomization module is additionally adopted; combustible vapor cloud explosion process model experiments in confined spaces of different structures can be also carried out; since various test sensors are installed in the installation holes of the device, and the five surfaces of the explosion device are all transparent, the combustion and explosion mechanisms of combustible gas cloud and steam cloud in the confined spaces of different structures can be researched with appropriate optical measurement technologies.