The invention discloses a positioning posture measuring method based on an inertial navigation system and a double-antenna GPS. The method is characterized by fixedly arranging the inertial navigation system INS and two GPS signal receiving antennas which are distributed in a geometrical structure and correspondingly arranging two receivers; carrying out linearization processing on a carrier wave phase double difference observation equation, using a CLAMBDA algorithm and applying a constrained condition to calculate a least square floating solution of a whole cycle ambiguity a, an estimation value of a baseline vector b and a variance-covariance matrix; simultaneously, using a unconstrained LAMBDA algorithm to search one least square method estimation solution aLLS, according to the estimation solution aLLS and the floating solution, calculating an initial search space size, and acquiring the whole cycle ambiguity a; and through a relation between position coordinates of an end point A and an end point B and a direction vector, solving two-dimensional attitude information of a carrier. The method has advantages that a data storage space is reduced; search efficiency of the whole cycle ambiguity is increased; and integral navigation precision and performance of the system are improved.