To increase comprehensive properties of cylinder steel, high-pressure cylinder steel 30CrMo-M was developed on the basis of steel 30CrMo. Tests and researches were made on factors which influence heat treatment properties, such as chemical composition, quenching temperature, and tempering temperature. The results indicated that the 30CrMo-M steel has stable chemical composition, its strength rises with increase of carbon equivalent, and thus it has better relativity. When concentration of quenching liquid is 5%, yield ratio of the steel can be guaranteed to be low, thus safety of cylinder is improved. Tempered between 570°C~622°C, the strength of the steel is increased and plasticity rises with increase of temperature. When tempered at 570°C, inner wall structure of cylinder contains tempering martensite, the strength is high but the plasticity is low. When tempered between 610°C~615°C, temper brittleness happens very easily and toughness is on the low side. The best heat treatment technology is: quenched at 930°C with temperature holding for 40 minutes and quenching liquid concentration as 5%, tempered at 580°C with temperature kept for 90 minutes. The microstructure treated by this technology is tempered sorbite with higher strength, plasticity and toughness.