Biology and ecology research in hadal zone (6000- 11000 m) has been a renewed interest recently. With advances in engineering technology, breaking the knowledge gap of hadal science becomes reality. Free-fall vehicle also known as “Lander” has been widely applied in marine investigation for decades. Achievements made in hadal field with landers have vastly encouraged scientists to implement further progress. This paper describes the design of a 7000-meter lander, which mainly focused on hadal biology and ecology research. Effort for oil filled compensation approach of powering and control subsystem has been conducted, which increases the reliability of pressure resistance and seal while reducing the size and weight of the sealed housing. Results of the high pressure test demonstrate the proposed approach is practical and reliable.