The invention belongs to the technical field of engines, and particularly relates to a method and system for evaluating a valve clearance adjustment cycle. The method for evaluating the valve clearance adjustment cycle comprises the steps that a variation range of the valve clearance is determined, and a variation model of the valve clearance is constructed according to the variation range; the current valve clearance of an engine is acquired, and when the valve clearance is not within the variation range, the valve clearance is adjusted; and the valve clearance adjustment cycle is determinedaccording to the variation model. According to the method for evaluating the valve clearance adjustment cycle, the variation rule of the valve clearance is obtained by constructing the variation modelof the valve clearance, the adjustment cycle can be determined according to the rule, and the valve clearance is adjusted according to the adjustment cycle, so that periodical adjustment of the valveclearance is achieved, the engine can be always kept in a good operating state, and the operating performance of the engine is improved.