The present invention provides a method for computing the parameter of tracer distributing in the living organism and diffusing in the ECS, comprising: measuring magnetic resonance signal increment corresponding to the different tracer concentrations (C) in agarose confirming the linear relation between the magnetic resonance signal increment and the tracer concentration obtaining the magnetic resonance images from different times after injecting the tracer with different concentrations into the living organism registering the MRI images and fitting the parameter of the tracer distributing in the living organism. The present invention can both obtain the structure of the response tissue cell and the diffusion parameters of physiological feature of living organism space in-vivo. Also, this method can reflect the tissue fluid flow and the diffusion parameters of the tracer in the distribution and clearance process through the tissue channel in the living organism.
