The invention, belonging to the field of calculating index of distribution network, the power supply capacity, in planning distribution system, relates to a method for the analysis of available power supply capacity of a medium voltage distribution network, comprising the steps: establishing an available power supply capacity mode; analyzing the communication relationship between main transformers in research area to form a main transformer communication relationship matrix Llink; according to the differences of in-station communication and inter-station communication, partitioning the matrix Llink and correcting the main transformer communication relationship matrix Llink; defining the elements of a capacity matrix R to represent main transformer capacity of corresponding communication center and correcting matrix R; calculating the available power supply capacity of the system; positioning weak points; and acquiring critical capacity. In the method for the analysis of available power supply capacity of the medium voltage distribution network according to the invention, the available power supply capacity calculation mode and the calculation analysis method are put forward, and on the basis of the available power supply capacity, the analysis method is put forward, in which the weak points in grid, which restrict the available power supply capacity, are rapidly positioned by channel-transferring bottleneck matrix, and the minimal element capacity required by communication line is obtained via the critical capacity.