The present disclosure provides a process for analyzing elements and mass ratios of elements of a tissue and a method for establishing a geometric model based on a medical image. The 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. The method for establishing a geometric model 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 tissue density； and generating the geometric model. By using the medical image data of the known tissues to analyze the elements and mass ratios of elements of a living tissue, the voxel phantom is more realistic to the real situation when made, thereby improving the accuracy of the dose calculation to improve the quality of treatment.
