Matrix formulation to describe the light propagation in stratified multilayered films has been extended to a system with phase incoherence. Several equations for the reflectance, transmittance, and light beam intensity in the film system are derived from the formulation. Some formulas previously proposed are corrected in reference to the present method. The beam intensity description is used for the calculation of light emissive power from multilayered films having a temperature gradient. It is found that the equations derived here are exactly equivalent to those derived from the radiative transfer equation. However, the present method is more tractable, and can be readily used for a film system with any number of layers.