The invention provides a high precision medium voltage distribution line true equivalent model and a parameter calculation method thereof. The model comprises A phase impedance used for simulating the self-impedance and mutual impedance of an A-phase wire, B phase impedance used for simulating the self-impedance and mutual impedance of a B-phase wire, C phase impedance used for simulating the self-impedance and mutual impedance of a C-phase wire, and G impedance used for simulating the earth return and interphase parameters. According to the invention, based on the power system analysis theory and according to the engineering practice of a distribution line, the influence of the transmission wires, among the wires and among the wires, the earth and the earth return and other factors are taken into account; an inverse-pi-shaped four-capacitor G impedance model structure is creatively provided to precisely simulate electromagnetic coupling among the wires and among the wires, the earth and the earth return; positive sequence and zero sequence parameters of the line are precisely simulated; and the cascade structure of multiple groups of lumped-parameter elements is used to meet the equivalent simulation of the distribution line of amplitude-frequency and phase-frequency response precision in a high frequency range.