Optical tweezers were used to study the dynamic process and the changing rule of the activity of the red blood cells in vitro.Red blood cells irradiated by the Gaussian beam of LD laser were deformed and reversed in optical tweezers.When the LD laser was cut off,the free recovery time of blood cells was obtained,which was associated with the cells′ activity.By comparing the decay process of cells activity between irradiated the red blood cells by low-power He-Ne laser and static red blood cells,the results showed:the cells activity presented a changing rule that,after fluctuations,it gradually declined till cells died.Irradiated by low-power He-Ne laser,red blood cells activity decreased slowly,namely laser irradiation postponed some decay stages.The results can provide valuable reference for the study of cells viability and dynamic analysis.