The invention discloses a compression ratio regulation and control device of a steam engine. The compression ratio regulation and control device comprises an air inlet pipeline clamping mechanism, theair inlet pipeline clamping mechanism comprises a clamping button and a clamping chuck, after a rubber pipe is inserted, rotating and clamping are performed, the clamping chuck is loosened by pressing the clamping button, the rubber pipe stretching into an interior can be clamped through the clamping mechanism and the locking mechanism, the rubber pipe cannot be withdrawn from a pipeline during inflation, the air tightness is good, air inflow can be controlled in a rotating mode, inletting air can be cut off when the air pressure in a storage cavity reaches a set storage air pressure, the regulation and control simplicity can be greatly improved, and the compression ratio regulation and control device is worthy of popularization.