The femtosecond pulsed laser is used to study the quantitative evaluation technology of the single event burnout (SEB) effect in GaN power devices. In this work, we establish two pulsed-laser effective energy transmission models for different device structures, analyzing and verifying the equivalent relationship between the effective laser energy and the heavy ion linear energy transmission (LET). The critical parameters of models are confirmed, including laser parameters and device parameters. The interface reflectivity between the layers is mainly considered. Meanwhile, the parameters are corrected by the multiple reflections between the interfaces, and the laser energy of the second reflection of the metal layer is considered. These measures can be used to reduce the error of the effective energy in the device active area. In addition, we validate the models experimentally. A gallium nitride high electron mobility transistor (GaN HEMT) and a schottky barrier diode (SBD) power device are used in the experiment on the irradiation by a femtosecond pulse laser. The effective laser energy thresholds and the laser equivalent LET threshold with two incident wavelengths of the SEB are calculated. The theoretical calculation value and the actual measured value are compared. The selcction basis of the laser wavelengths is given by the detailed study. The support for the laser quantitative evaluation and the protection design of the SEB in GaN power devices is provided by this work.