Under the condition of the poor quality of the satellite signal, we can not through the observation equation to solve the ambiguity and unable to real-time accurate the distance measurement, so a method using inertial information to calculate the ambiguity is put forward, which is a kind of carrier combined the movement inertial navigation information with the relative baseline measurement information, and then realize the precision dynamic relative positioning algorithm between the two carriers. Through the establishment of double difference carrier phase observation equation and inertial navigation observation equation tight combination, respectively in depending on the number of satellites are more than four and four conditions to solve the ambiguity of unknowns. Finally, through constructing integrated test system platform, the use of field vehicle test completed the positioning accuracy of combination system test, the results show that the combined system positioning accuracy compared with the original single GNSS positioning accuracy must be improved.