A absorbent unit comprises branch gas pipe, active carbon, filter ball, multi hole plate, gas pipe, filter net, chemicals, shell, inner fin and outer fin. Producing process follows: shell welding, water pressure test, plate welding, chemicals input, drying, plate holing, gas pipe fixing, drying and activation, vacuuming, nitrogen injection, sealing. The unit is driven by the heat of exhausting gas from diesel ship. By heating and cooling in turn, absorbing and desorbing will be realized then the cooling of the motor set. The unit has three layers of filter of active carbon layer, stain steel net layer and filter balls layer, which will keep the chemical circulate inside the unit without affection to the system and keep its utility as well. The inner and outer fins increase the efficiency of heat exchange.