The invention discloses an integrated modeling method for an infrared radiation characteristic of a complicated target. A bidirectional reflection distribution function model of infrared radiation on the surface of the complicated target and an infrared radiation model of non-uniform tail flame gas are considered based on a radiometry spectral ray tracking method; in a ray tracking process, the pixel on the focal plane of a detector is sampled, thus generating ray bundles, and an intersection between each ray and the complicated target in a scene is calculated; a radiation reflection value of each intersection is calculated, and the radiation brightness obtained by all the rays of the pixel is subjected to sampling and reconstruction, thus obtaining the radiation brightness with a spectral form at the pixel of the detector; finally, a required infrared spectrum band is integrated, thus obtaining a target infrared radiation characteristic value received by the detector. According to the integrated modeling method, the spectral ray tracking method runs through the whole solving process, and a solving model suitable for a ray tracking form is constructed, so that the integrated modeling method is suitable for infrared radiation characteristic simulation of a tail-flame-containing complicated target aircraft under a specific flying state.