The invention discloses a method for cleaning of a flat slice for bonding of a cylindrical blank of an optical lens, which is characterized in that alkali solution is used as a cleaning medium, an ultrasonic cleaning machine is adopted as a cleaning device, the alkali solution with a pH value being 10-11 is heated to be at the temperature of 95-105 DEG C, and the cleaning time is 2-3 minutes. The method has the advantages of short cleaning period, good cleaning effect, high work efficiency for production and the like. Simultaneously, the method also has the advantages of saving auxiliary materials and avoiding environmental pollution.