According to acoustic/dead-reckoning integrated positioning system of underwater vehicle, the positioning geometric structure among acoustic beacons and underwater vehicle is used to construct the equation and inequality constraints of underwater acoustic range measurements. By combining the maximum a posterior(MAP)estimation criterion with standard extended Kalman filtering(EKF)method, an integrated positioning algorithm for underwater vehicles under the constraints of acoustic range measurements is designed, which achieves the effective integration of underwater acoustic range measurements and dead-reckoning information. Numerical simulation results show that the proposed integrated positioning algorithm can effectively utilize the underwater acoustic range measurement information to improve the positioning accuracy of underwater vehicle.