The thermal effect of metal spherical shell irradiated by invariable power density laser was calculated using finite element method. The variety rule for temperature rise and temperature difference of inwall and outerwall was analyzed, also the metals of copper and aluminum were taken for example, and the temperature variety and response time of the copper spherical shell irradiated by laser were compared with the aluminum spherical shell. The results indicate that, when the transitional process finishes, the temperature rising speed of inwall and outerwall is almost a constant, and the temperature difference of inwall and outerwall keeps constant during laser irradiation. When the laser irradiation stops, the heat balance process between inwall and outerwall will be done within tens of milliseconds to one second for the copper and aluminum spherical shell with thickness from 0.004 m to 0.02 m.