Abstract: Small loop transient electromagnetic method (TEM) is a widely used electromagnetic exploration method in mountainous areas, tunnels, underground coal mines and other areas with difficult construction arrangement. The self-inductance and mutual inductance of the coil are prominent because this method increases the number of turns of the loop and then increases the emitted magnetic dipole moment to increase the detection depth and improve the anti-interference ability. However, the self-inductance and mutual inductance between multi-turn loops often cause severe distortion of early signals measured by TEM, resulting in generally low apparent resistivity. The calculation formulas of self-inductance and mutual inductance for rectangular coils and circular coils are analyzed and summarized, and the corresponding self-inductance and mutual inductance values and their relative errors are calculated respectively when the coil side length or radius is 1 m to 5 m, and the applicability of various calculation formulas is analyzed, and an appropriate calculation formula of inductance for small loop is given.