Based on the technology of ram-type quick airdrop rigid air chamber, diameter adjustable air inlet mechanism was designed, which mainly included batteries, spring, electromagnet, and variational resistance. Three-dimensional mathematical model of the air inlet was established. Built-in manometry mechanism for cushioning equipment and pressure testing system project was designed according to pressure testing requirement of quick airdrop conditions. The system has simple structure, easy maintenance, small volume and small mass characteristic, and they satisfy application requirements of quickly airdrop system.