The disclosure provides an experimental calibration method of a redundant inertial measurement unit including, step (1), establishing an installation angle model using a cone descriptive scheme, and obtaining a relationship of an angular speed of a carrier and an angular speed measured by each gyroscope, step (2), establishing a standard calibration model of the redundant inertial measurement unit based on a relationship between a sensor coordinate system and a carrier coordinate system, step (3), establishing a state equation and a measurement equation of a filter, step (4), performing a row amplification of measurement amounts based on the measurement equation established in step (3), and obtaining an amplificated measurement equation for improving observability, and step (5), obtaining a Jacobi matrix and a Hessian matrix based on the amplificated measurement equation, and estimating error parameters by an extended Kalman filtering algorithm based on a second-order Taylor expansion.