Provided are a method and apparatus for compensating an attitude of an inertial navigation system and a method and apparatus for calculating a position of the inertial navigation system using the same. The method of compensating an attitude of the inertial navigation system includes sensing movement of the system and outputting information for stoppage time periods and a movement time period of the system; receiving angular velocity information of the system during every time period and calculating a first attitude of the system using the angular velocity information; receiving gravity direction information of the system during the stoppage time periods, calculating a second attitude of the system using the gravity direction information, and calculating an attitude error of the system during every time period using the first attitude and the second attitude; and compensating the attitude error for the first attitude.