Abstract: In this paper,pectin was extracted from pineapple peel using Ammonium oxalate method assisted by ultrasonic, four factors such as Ammonium oxalate concentration,precipitation agent pH value,extracting solid-liquid ratio and extraction temperature which effect on pectin extraction yield was investigated separately.Orthogonal test was utilized on the basis of results of single-factor test.Through comparing R and K value,it could be concluded that precipitation agent pH value had great influence on pectin extraction yield.The best experiment scheme was reached that precipitation agent pH value was 3.5,Ammonium oxalate concentration 7g·L-1,extraction temperature 75℃ and extracting solid-liquid ratio 1∶30.The pectin exacting yield could reach 7.32%.FT-IR spectroscopy of pineapple rind pectin suggested that absorption peak on 1 051cm-1 was caused by acetyl groups and peaks density contrast on 620cm-1 and 1 749cm-1 indicated that pineapple peel pectin was a low ester pectin.