In order to meet the requirements of high-quality deep seabed sediment pressure-maintaining sample during the scientific researches of deep seabed under full sea depth, a mechanical hand-held device with pressure-maintaining function was designed in accordance with the maneuverability of the manned submarine operations. The key components such as pressure-maintaining container and pressure compensation device of sediment airtight sampler under full sea depth were analyzed and calculated. Finite element simulation analysis was performed under full sea-deep pressure environments. The results show that the stress and strain of the airtight sampler increase with the increase of the applied pressure, the maximum stress and strain appear at the sealing positions of the end cap and the cylinder seal, and stress and strain are small in the contact positions of the square stopper and the pressure-maintaining cylinder end caps with good sealing performance. Finally, the internal pressure tests and the manipulator cooperative adaptability tests of the full sea-deep sediment airtight samplers were carried out. The results of tests verify the feasibility of the pressure-maintaining performance and the adaptability of the manipulator for the full sea-deep sediment airtight samplers.