The inductance coefficient of a multilayer tightly wound rectangular circular coil is divided into self-inductance of all single-turn coils and mutual inductance of any two coils, and then the sum of all self-inductance and mutual inductance of the entire winding is obtained. Using Neumann formula and numerical integration software, the inductance coefficient of the multilayer close-wound rectangular section circular coil with an average radius of 10 cm is calculated to be 4.65 mH, while the inductance coefficient of the actual coil with the same size measured by inductance meter is 4.66 mH. The theoretical calculated value is basically consistent with the experimental measured value, and the relative error of the two is only 0.22%. It provides theoretical reference for designing inductance coil.