The thermal mechanism of the transition from the superconducting to normal state as a result of the superconducting film heating by a strong electromagnetic wave has been theoretically investigated. The thermal balance equation for a thin film on dielectric substrate, stabilized at a temperature T₀ is solved. The absorption of radiation in the film is calculated using a two-fluid model of a superconductor. The hysteresis character of the S-N transition is shown. The MW and IR power limiter is proposed. The limiter is a superconducting film mirror, which limits the reflected power. The dependences of the threshold value of incident power against T₀ for some frequencies are calculated.