Abstract: For the fault detection difficulties of the natural gas compressors' engines caused by the coupled detection signals interference, a fault diagnosis method was adopted combining the units' action event and sub-band fault signals detection based on the crank angle. The fault type can be diagnosed accurately by analyzing the detection signals combining fault diagnosis and the units' action events, installing the fixed magnetic velocity sensor on the crankshaft, and establishing units action events based on the crank angle. ZTY310 MH performance tests of a booster station is taken as an example. Result of the detection verifies that the ignition angle improper and carbon deposit are the real reasons for engine working inferior. Detecting regularly for the engine of reciprocating compressor can be helpful to discover and diagnose faults as soon as possible and also reduce the security risks and downtime. Therefore, it is of great significance to improve the working performance of the engine of natural gas compressors.