The invention relates to the technical field of simulated light source measurement, in particular to a mechanical skeleton of a target simulator, which is applied to passive target simulators. During use, the mechanical skeleton of the target simulator is bounded on a corresponding aircraft. The mechanical skeleton comprises more than two assembled blocks. Each assembled block comprises an internal plate, an internal plate housing and a cavity defined by the internal plate and the internal plate housing. Two adjacent assembled blocks are hinged together through a corresponding hinging shaft, so that the mechanical skeleton has a chain-like structure. A connector is arranged between the assembled blocks at the two ends and used for locking the assembled blocks. Receiving windows and emission windows are formed on the mechanical skeleton. The receiving windows and the emission windows are in one-to-one correspondence and all formed on the internal plates of the corresponding assembled blocks. Collimator mounting holes are formed in the receiving windows and used for mounting light receiving collimators, and coupler mounting holes are formed in the emission windows and used for mounting light emission couplers. The problem that the existing target simulators are poor in synchronous processing of system pulse signals and replaceability of parts can be solved.