The invention discloses a compilation optimization method for loongson-based 3A vector memory access. The method provided by the invention is characterized by comprising the following steps: adding an expansion path from a vector tree structure to intermediate representation, and transforming the vector tree structure into corresponding intermediate representation; in the process of expansion, carrying out expansion along an original path when a normal mode is adopted; carrying out expansion is carried out along a new path when a vectorization mode is adopted; for loop containing public operation variables, creating an assignment chain by utilizing the generated intermediate representation, and updating the operand of the assignment chain; after expansion from the tree to register transmission language (RTL) representation, adding an optimization pass for a pass_replace_reg; and in a rear-end instruction description file of a compiler, adding rear-end instruction description of a vector instruction, and automatically translating the generated intermediate representation into an assembler instruction by the compiler. By using the method provided by the invention, the compiler can automatically generate a high-performance vector memory access instruction, thereby saving manual compilation of programmers and greatly improving the operation efficiency of application programs.