The invention provides a non-welding assembly method of a multistage depressed collector assembly. The method comprises the following steps: axially dividing the whole ceramic cylinder into N circular arcs according to the stage number N of collectors; arranging at least one groove for locating collector electrodes on an inner cambered surface of each circular arc; forming a through hole for mounting leads of the collectors on each circular arc; and arranging N circular arcs around the multistage collectors to form the ceramic cylinder, locating a flange on the electrode of the collector of each stage and the corresponding groove in the circular arc in a fit manner, leading out the leads of the multistage collectors from the through holes, and placing the ceramic cylinder formed by the circular arcs in a collector outer sleeve so that the multistage collectors, the ceramic cylinder formed by arranging the circular arcs and the collector outer sleeve are tightly assembled together. By means of the non-welding assembly method provided by the invention, the problems such as heat dissipation, insulation, reliability and service life of the traditional multistage depressed collectors can be solved.