It was proposed to apply the accelerometer module JY901 to measure the contacting bottom and penetration depth in a compact submarine insitu stratified observation system device.The contacting bottom and penetration depth calculation algorithm was designed,and simulation calculation was performed to verify algorithm and error in MATLAB.The displacement measurement was carried out on the motion platform by using the accelerometer.The measurement error is about 5%.The iron rod falling freely into sand was used to simulate the process of the seafloor insitu stratification system penetrating the sediment.The use of accelerometer sensors to detect contacting bottom has been proven feasible,and the measured penetration depth error is about 10%.The research provides a motion state detection method for the seafloor insitu layered observation system without adding additional sensors.