A process for analyzing elements and mass ratios of elements of a tissue includes approximating the tissue having unknown elements and mass ratios of the unknown elements thereof using the data of the medical image corresponding to a tissue having known elements and mass ratios of the known elements thereof. A method for establishing a geometric model based on a medical image includes: reading data of the medical image； defining a type of a tissue according to a conversion relationship between the data of the medical image and tissue types or according to the process； determining a quantity of tissue clusters of the tissue； defining a tissue density of the tissue by a conversion relationship between the data of the medical image and density values； establishing a 3D coding matrix with information about the tissue and the density； and generating the geometric model.
