This paper presents Crossover Tabu Search(CTS),an improved tabu search,which adopts the crossover operator of the genetic algorithm as the diversification strategy to drive the search into new regions to exploit the new search space.To test its performances,CTS is applied to solve the integer ambiguity-searching problem of a Double Global Positioning System(DGPS).First,a null-space restriction is used to define the searching space,and then,CTS is applied to search the optimal result of the integer ambiguity in the searching space.The best result of a practical measurement example is that the searching reliability can reach 92% for a searching ratio of 6%,and the searching reliability is only 45% for the same searching ratio while the traditional tabu search is used.Experimental results show that CTS improves the performance of the traditional tabu search.