The mathematical starting point of mathematical problems and the axiom of solving process. Simplicity refers to the symbol of mathematical language, the axiom of mathematical starting point and the beauty of simplicity in the process of solving mathematical problems. First of all, mathematical language is a simple and unified language symbol. Secondly, the starting point of mathematics is axiom, simple and clear. Finally, solving mathematical problems is also a process of simplifying. Mathematical beauty includes simplicity, symmetry, harmony, unity and strangeness, and simplicity is a feature of mathematical beauty.