Abstract: We used the RPHA method to test the human blood stain. It appers high specificity as it test with pig, cow as well as other 6 kinds of animal blood solution. The minimun quantity of detectabl human Hb is 6.48ng. Synthetic detergent does not interfer with this method. Put the sand, cloth and rusty iron with human blood in 37℃ for 15 days, there is no influence to the result. The method is simple and accurate without any special instruments and reagents.