The fire-extinguishing capability of aqueous film-forming foam(AFFF) is usually evaluated by actual fire-fighting test.It is not only costly,but also unfavorably to environment and safety.Therefore,it is of importance to find means to evaluate the performance of AFFF indoor.In this work a simple laboratory method for evaluating the performance of AFFF is proposed,based on the principle of AFFF and our researches on AFFF.It is found that the fire-extinguishing capability of AFFF could be evaluated by five parameters.1) spread ability of AFFF on the oil,2) the spread amount of AFFF on oil,3) foaming ability of AFFF,4) speed of liquid eduction from foam,5) stability of foam.These parameters can be measured easily in common laboratory,by which the fire-extinguishing capability of AFFF can be evaluated without actual fire-extinguishing test.