The ultrasonic assisted extraction of pigments from Polygoni cuspidate and their stability were studied.Ethanol was used as a solvent,extraction yield and color value were treated as a evaluation indicator.The solid-to-liquid ratio,extracting temperature,ultrasonic power,extracting time,and the volume fraction of ethanol were studied to determine the effect on the extraction by single-factor test.The extraction technology was optimized by the orthogonal test and the stability of pigment obtained was also in...