To analyze the effect of different magnetic field strengths on blood in vitro at different temperatures and provide ideas for the research on the effect of different magnetic fields on blood.Methods:Rats were randomly divided into a room temperature group(25 ℃) and a low temperature group(0-4 ℃).In each group，geomagnetic group(GMF)，hypomagnetic field group(HMF)，strong magnetic group(SMF)，and extremely strong magnetic field group(ESMF) were set up.Immediately after 2 h of treatment，serum samples were collected and the levels of glutamic-oxaloacetic transaminase(GOT)，glutamic-pyruvic transaminase(GPT)，superoxide dismutase(SOD)，and 2,3-diphosphoglycerate(2,3-DPG) were measured.Results:ESMF at room temperature for a short time(2 h) was able to cause a significant decrease in GOT activity(P<0.01) and a downward trend in GPT activity.The low temperature might enhance the effect of each magnetic field on GOT and GPT.HMF，SMF，and ESMF at room temperature and HMF and SMF at low temperature caused an upward trend in 2,3-DPG，and ESMF at low temperature was able to significantly lower 2,3-DPG(P<0.005).There was no effect of each magnetic field on SOD at different temperatures.Conclusion:HMF can protect the in vitro blood protease activity in a short time，and the negative effect of ESMF should be avoided in the transport of blood samples.The findings of this study are expected to provide a necessary basis and references for revealing the mechanism of the magnetic field effect and the technological development of blood sample preservation in clinical and scientific research，which has certain theoretical significance and application value.