Cell growth is regulated precisely by many nutritional and growth factors. Protein is the most abundant macromolecular substance in the cell. Amino acid, as its metabolic substrate, is involved in many important physiological processes including protein synthesis. Moreover, amino acid, as a vital signaling molecule, is also important in the regulation of many pathophysiological changes. In recent years, studies have paid more attention to nutritional sensing and its pathophysiological significance. As the vital role in the cell growth, amino acid sensing has received the most attention. mTORC1 is the key sensing signaling in amino acid sensing. The precise sensing of amino acid in the cell is important to the normal functions of mTORC1. Many amino acid sensors, including amino acid transporters, taste receptors and GCN, mediate amino acid signaling, regulate the mTORC1 activity, and are associated with the process of amino acid sensing. More importantly, the dysregulation of mTORC1 on the amino acid sensing play an important role in the proliferation and metastasis of malignant tumor. More and more studies show that the amino acid sensor and its mediated mTORC1 regulation may be a potential target in the treatment of cancer. In this article, we review the functions of mTORC1 in the regulation of amino acid sensing and its role in the development of malignant tumor.