Abstarct: determining the attitude of the vessels is vital. Aim of this study is determine the precise angles of the inertial navigation system . With development of micro electromechanical systems (MEMS),in this paper a new method is proposed baxsed on this technology which uses integrated sensors including a gyroscope, accelerometer and three-axis magnetometer, a device is designed to determine the attitude. first the navigation system connected to body receive information from sensors and with processing it in reference coordinate system calculate attitude angles . it is lightweight and have small size relative to the previous ones and can be used in commercial and military applications .by combining these three sensor output we obtain three-axis and by using Whba theorem and solving navigation system equations we determine the attitude and heading. the sensor outputs have noise and error we calculate these noise using "Allen Variance" and random walk then these noise filtered using a Kalman filter. then by using appropriate calibration algorithms,produced constant errors such as bias,scale factor and misallienment of sensors axis measured and removed. Also for the calibration of the magnetometer sensor which is sensitive to environmental and mextals conditions and should be calibrated online, a method is provided that does not require the use of clear situations. Finally, drifts created by the passage of time and the remaining bias in the gyroscope calibration estimated in the Kalman filter and removed. Static and dynamic tests done on the designed system which show precision of less than 0.5 degrees and for roll and twist angles show accuracy of less than 0.2 degrees.