Objective To investigate the protective effects of cardioplegic solution with creatine phosphate on donor heart preservation in rats, and the possibility of prolonging outofbody heart preservation in lack of blood supply to improve on transplantation quality. Methods Twenty Wistar rats were randomly divided into two groups, control group (n=10): pure St.ThomasⅡ cardioplegic solution was perfused to protect donor hearts; experimental group (n=10): St.ThomasⅡ cardioplegic solution with 2.5g/L sodium creatine phosphate was perfused to protect donor hearts. After 4 hours of refrigerated preservation, myocardial tissues were tested for adenosinetriphosphate(ATP) level and super oxide dismutase (SOD) activity. Cardiac ultrastructure and mitochondria swelling condition were monitored with light and electron microscopes. Results After the 4hour low temperature preservation of donor hearts, ATP content in experimental group cardiac tissue was significantly higher than that in control group (2.75±0.99μmol/mg vs. 1.77±0.86μmol/mg, Plt;0.05); SOD in experimental group cardiac tissue was significantly higher than that in control group（49.6±2.52 U/mg vs. 45.27±2.21 U/mg，Plt;0.05）. Electron microscopic inspection demonstrates that in the control group, chromatin condensed and dissolved inside the nuclear membrane; mitochondria ridge gap disappeared; myocardial cell pyknosis and mesenchymal vascular endothelia necrosis appeared. In contrast, myocardial cell nuclei remained in the center; sarcomere band structure was distinct; sarcoplasmic reticulum expanded and intercalated disk band structure was clear in experimental group. Conclusion Cardioplegic solution with creatine phosphate is able to enhance donor heart myocardial protection significantly.