Working principle: When the liner under the pump is long or there are downhole tools such as packers under the pump, the pump body is stressed. If a full barrel pump is used, the barrel will deform, shrink in diameter, and reduce the actual seal gap. The pump barrel of the suspension pump is not affected by the gravity of the microtube and the downhole tool. The stress conditions are: gravity of the pump tail pipe—lower joint—outer pipe —upper joint—upper pipe —wellhead.