This paper presents a novel SINS/IUSBL integration navigation strategy for underwater vehicles.Based on the principle of inverted USBL(IUSBL),a SINS/IUSBL integration navigation system is established,where the USBL device and the SINS are both rigidly mounted onboard the underwater vehicle,and fully developed in-house,the integration navigation system will be able to provide the absolute position of the underwater vehicle with a transponder deployed at a known position beforehand.Furthermore,the state error equation and the measurement equation of SINS/IUSBL integration navigation system are derived,the difference between the position calculated by SINS and the absolute position obtained by IUSBL positioning technology is used as the measurement information.The observability of the integration system is analyzed based on the singular value decomposition(SVD)method.Finally,a mathematical simulation is performed to demonstrate the effectiveness of the proposed SINS/IUSBL integration approach,and the observable degrees of the state variables are also analyzed.