The optimal extraction process and stability of natural red pigment from Red amaranth were studied.Methods:The optimal extraction process was obtained by means of single-factor test and orthogonal test.The stability under different conditions such as pH,light,temperature,common metal ions,H2O2,VC,sugar were analyzed.Results:Natural red pigment in red amaranth belongs to the anthocyanins.The optimal parameters for extraction process were: ratio of solid to liquid 1∶ 25,extraction for 4h,at 45℃.The anthocyanins(counted by Cyanidin-3-O-glucoside chloride) content was 3.534 mg/100mL detected by pH-Differential spectrophotometry.The red pigment was unstable under conditions of pH≥12,sunlight,high temperature,Al3+,Fe3+,Cu2+,oxidant.Conclusion:The natural red pigment from Red amaranth was extracted by ethanol.More research is needed on its stability used as a food additive.