The invention discloses a technology for extracting a nano level coloring agent from plants. The technology comprises the following steps: (1) grinding plants, adding plants into an acid solution, wherein the mass ratio of plants to the acid solution is (1-3):(1-3), evenly stirring, allowing the system to stand still for 30 to 90 minutes, and filtering to obtain an acid hydrolyzed material; (2) adding the acid hydrolyzed material into water, adjusting the pH to 3-10, then carrying out ultrasonic extraction, wherein the mass ratio of acid hydrolyzed material to water is 1:10-1:50, the ultrasonic frequency is 10 to 80 KHz, ultrasonic extraction is carried out for 15 to 25 minutes at a temperature of 38 to 42 DEG C, then ultrasonic extraction is performed for 5 to 15 minutes at a temperature of 88 to 92 DEG C, and finally ultrasonic extraction is carried out for 25 to 35 minutes at a temperature of 18 to 22 DEG C, filtering, and collecting the filtrate; (3) condensing the filtrate, and freeze-drying the condensate; (4) performing ultrafine grinding. The provided nano level coloring agent extraction technology has the advantages that the equipment requirements are low, the technology is simple, the extraction efficiency is high; the obtained coloring agent is completely natural, is safe to human body, and can be widely applied to textile dyeing and human skin dyeing (eyebrow dyeing, lip dyeing, eye lien dyeing, etc.).