Provided is a lightweight method of a super-large three-dimensional model of a carrier rocket. The method comprises the steps that 1, conventional part three-dimensional modeling is conducted on the carrier rocket in a Creo environment; 2, chemical milling plate wall part molding is conducted; 3, porous part modeling is conducted; 4, assembly three-dimensional modeling is conducted on the carrier rocket in the Creo environment; 5, an instrument is installed on a rocket body, cable laying is conducted through a skeleton, and a reference relation of a cable laying path and a reference model is disconnected; 6, except mechanisms, parts are made to be completely positioned in assemblies; 7, a model rotating detail control function is enabled; 8, an assembled rocket model is subjected to sectional interference checking, screening is conducted on each section of the related assembled rocket model, interference volume is calculated for model obtained after screening, if interference exists, the interference-related model is redesigned, and the steps are executed again from the first step.