Abstract: The LAMBDA method needs to start with a float solution to the ambiguities, and several epochs are needed by only using phase measurements and it will take a long initial time. To deal this problem, with the special transformation of global positioning system (GPS) carrier phase single difference observation equation of short baseline, new observation equations in which the unknown integer ambiguities are treated as noise could be obtained. Combining them with the original equations, it is possible to get a float solution using only one epoch for that the equations have redundancy. And it changes that the floating solution can not be obtained in a single epoch by only using double difference phase observation equation. In-depth study through the float solution and fixed solution from the LAMBDA algorithm, a new method which can fix the low precise float ambiguity to the correct integer ambiguity was given. It reduces the dependency of the high precise float resolution for LAMBDA method which needs many epochs to obtain, so the integer ambiguities can be estimated in single epoch and single frequency. The success rate is more than 97% in actual testing. The results show that the new method can be effectively used for real-time calculation of kinematic attitude.