According to the problem of prolonged navigation error accumulation without external information in vehicle inertial navigation system, a method of improving the navigation accuracy by using the dynamic zero velocity update technology was proposed. The observables were constructed by using the constraint conditions of the zero velocity update technology. First, the theory of spectral condition number was used to analyze the observability of error states and determine the effect of Kalman filter, then the attitude angle error, rate errors were estimated though the simulation experiment. Experiments showed that, in the inertial navigation system, zero velocity update technology improved the navigation position, velocity, attitude information greatly and effectively ensured the accuracy of vehicle navigation.