A latitude unknown self-aligning method of a strapdown inertial navigation system under the dynamic interference condition includes the steps that firstly, a geometrical analytic formula is built by means of the characteristic that the projection of gravity acceleration is unchanged in an inertial coordinate system, the gravity acceleration is subjected to integration to obtain speed information, and the latitude value of the position where a carrier is located is calculated according to the speed information; secondly, on the basis of the double-vector altitude determination principle and by means of the characteristic that the gravity acceleration of an inertial system includes north orientation information, rough solution of an initial attitude matrix under the inertial system is achieved; finally, on the basis that coarse alignment is finished, a precise alignment error model under the latitude unknown dynamic interference condition is built according to a speed error equation, a misalignment angle equation and a latitude error equation, the latitude error angle and the misalignment angle of the carrier are calculated by means of the self-adaptive filtering method based on information, the latitude value is compensated with the latitude error angle, the strapdown altitude matrix is corrected according to the misalignment angle, and high-precision quick self-aligning of the strapdown inertial navigation system is achieved.