Aiming at the problem that when pseudorange observation noise was high, and the ambiguity calculation of TCAR(three carrier ambiguity resolution) method was unreliable in the condition of kinematic-to-kinematic, a triple-frequency kinematic-to-kinematic ambiguity resolution with BDS/INS tightly-coupled integration was proposed. Replacing the double-difference pseudorange observations in GF(geometry-free) and GB(geometry-based) patterns with the double-difference geometry distances estimated by the tightly-coupled integration system, the method obviously decreased the noise level of the pseudorange double-difference observations and improved the success rate of triple-frequency ambiguity calculation. Simulation results show that, the high-precision position output of BDS/INS tightly-coupled integration improved the accuracy of pseudorange observations by more than 60%. In short-baseline condition, when the pseudorange observation noise is 2 m, the success rate of triple-frequency integer ambiguity calculation by GF-TCAR is 0.73% while 31.25% by GB-TCAR. However, the integer ambiguity calculation success rate by the new TCAR method is beyond 99%. And this new solution can achieve centimeter-level kinematic-to-kinematic relative positioning.