Abstract: The metric thrust jet-effects testing methodology is introduced in FL-3 wind tunnel. Different from the sleeve type jet-effects testing methodology, the airframe is integrated with the nozzle by using the bellows system, and the balance can measure simultaneously the aerodynamic characteristics and the nozzle thrust. The problems such as nozzle geometric incomplete similarity, touching possibility between the model and the nozzle, imprecise modification of the pressure in the model cavity, etc, which exist in the sleeve type jet-effects testing methodology can be avoided by using the metric thrust methodology. The similarity theory, testing methodology and bellows technology of the metric thrust jet-effects testing are discussed in detail in this paper. The experimental results show that jet-effects under different test conditions including different nozzle pressure ratios and vectoring jets can be gained by the metric thrust jet-effects testing methodology. After further improvements of some details, the test capability can be enhanced, and the nozzle performance wind tunnel testing methodology and the thrust vector wind tunnel testing methodology can also be developed based on this methodology.