The aim of this observational study is to comprehensively analyze the metabolites in plasma samples from multi-cancer patients using advanced mass spectrometry detection technology, in conjunction with metabolomics approaches. The goal is to construct a plasma metabolite database for multi-cancer patients. Simultaneously, we will delve into the exploration and validation of a series of metabolic biomarkers for early multi-cancer diagnosis. The objective is to establish a safer, more convenient, and more sensitive early screening method, thereby providing a reliable scientific foundation and critical evidence for improving the early diagnostic process for individuals at high risk of multi-cancer.