Silk relics are valuable materials for studying the ancient embroidery technology, culture and art history of' China. The protection of the silk relics is of great significance to China’s cultural relic status. However, silk relics may be polluted by blood as the bodies decay and as the environment in the graves changes. Blood stains, having low solubility and being closely attached to the silk, made cleaning difficult. So the choice of the right detergent for removing the blood stains with minimal mechanical agitation becomes critical for the conservation of silk relics. This research investigated the cooperative effects of using a protease and a surfactant to remove blood stains. First suitable proteases and surfactants were screened. Then the cleaning parameters, such as dosage concentration, soaking time and soaking temperature, were optimized. The results showed that the optimal protease and surfactant are Savinase and alkyl polyglycoside (APG) respectively. The optimal concentration of Savinase is 1 % and that of APG is 5%. The best of the soaking time and soaking temperature were 30 min and 50 [degree]C respectively. After treatment, scanning electron microscope (SEM) and tensile strength tests were used to check the cooperative cleaning effects of Savinase and APG. The results showed that there was little impact on the silk’s structure and tensile strength after cleaning. This cleaning technology was applied to silk fragment relics of Yuan Dynasty, with good results. This research provided a new mild method to remove the blood stains on silk relics.