Abstract: Based on BDS measured data，three pairs of linear independent extra wide-lane(EWL) combinations were selected. Then，single epoch ambiguity resolution was carried out with these selectedcombinations using the combined geometry-free(FG)and geometry-based method(GB).After this treatment，the original phase ambiguity of each frequency can be resolved. Finally the ambiguity resolved phase measurements are used for precise positioning. Experimental results show that for short baseline situations，reasonable selection of the combination coefficients is decisive for a high success rate in ambiguity resolution. If the coefficients are selected correctly，the success rate of single epoch ambiguity resolution for original phase measurements is 99. 75% in the static mode and 95. 08%in the kinematic mode，so that the traditional exhaustive data preprocessing，such as cycle slip detection，can be avoided and a centimeter level positioning result can be achieved reliably.