The invention discloses a pressure boosting and maintaining device for an engine lubricating system. The pressure boosting and maintaining device comprises a crankshaft (3), a bearing oil seal (1), a crankcase bearing (2), a crankshaft oil seal (31) and a main oil gallery (32), which are arranged in a left crankshaft body (4). The bearing oil seal (1) is connected with the crankcase bearing (2) and the left crankshaft body (4) in an interference fit manner. The crankshaft oil seal (31) is connected with the crankshaft (3) in an interference fit manner. The bearing oil seal (1) and the crankshaft oil seal (31) are correspondingly arranged on two side surfaces of the main oil gallery (32). The pressure boosting and maintaining device has the advantages that the structural design is reasonable, the cost is low, the pressure of lubricating oil can be improved from 0.2 MPa to 2.5 MPa, the pressure is maintained to be 1.5-2 MPa, the lubricating and radiating effects of the variable speed part of an engine, a crankshaft assembly and a piston cylinder are effectively improved, and the operation reliability and the operation stability of the engine are ensured.