The invention discloses an installation method of a primary loop main pipeline of a nuclear power plant. The method comprises the following steps: 1) a pressure vessel and pump shells of main pumps are mounted in place; 2) the main pipeline is mounted in place and is in welding connection with the pressure vessel and the pump shells of the main pumps, and the main pipeline comprises main pipeline cooling sections, main pipeline hot sections and main pipeline transition sections; and 3) steam generators are mounted in place and are welded with the main pipeline, and the installation of the primary loop main pipeline is completed. Compared with the prior art, the installation method of the primary loop main pipeline of the nuclear power plant adopts the construction scheme of after-mounting of the steam generators, eliminates effects of the delay of steam generator manufacture on on-site welding of the main pipeline, and is beneficial for control of the on-site construction progress.