As a highly reliable positioning and orientation equipment, the redundant inertial navigation system (INS) is widely used in aerospace and other fields. For INS, high-precision calibration is the basis of high-precision navigation. Different from the calibration error modeling method of traditional orthogonal system, the nonorthogonal redundant ring laser gyro INS is installed with multi-device obliquely, and with the complexity of the configuration, the difficulty of separating the calibration parameters is also increased. Therefore, it is very significant to find a high precision calibration scheme for the non-orthogonal redundant INS. In this paper, the high precision calibration of non-orthogonal redundant INS in laboratory is studied, and a new calibration model of redundant system is summarized. A regular tetrahedral configuration prototype consisting of four Ring Laser Gyro and four Quartz Accelerometer is designed, and the calibration error modeling method and calibration accuracy are verified.