Abstract: Aiming at the problem in the conventional GPS single epoch data processing if no priori information, a new algorithm for solving GPS integer ambiguity using single epoch data was proposed. It used one epoch code observation to calculate initial ambiguity by least square method. The original search space of ambiguity was constructed by using standard deviation of the initial position. The ambiguity transformation by using two different linear combination of expansion wave was carried out to make the original search space of ambiguity smaller. After the new search space of ambiguity was confirmed, ambiguity N₁ and N₂ were solved by means of the inverse linear transformation. Furthermore, ambiguity function method was used for the searching of the true value using single epoch data.Two sets of data with different baseline length was used for analysis and test. The experimental results show that the proposed method was feasible and reliable.