The invention relates to an infrared photoacoustic spectroscopy detection device and method for decomposed components of sulfur hexafluoride under partial discharge, belonging to the technical field of partial discharge on-line monitoring of SF6 gas insulating electrical equipment. The device of the invention mainly comprises an induction voltage regulator, a corona free experimental transformer, a partial discharge free protective resistor, a standard capacitive voltage divider, a non-inductive resistor, a GIS analog element, a wide-frequency high-speed ultrahigh-capacity digital storage oscillograph and an infrared photoacoustic spectroscopy system. In the method of the invention, infrared photoacoustic spectroscopy detection is carried out on the decomposed gas of SF6 under partial discharge in the GIS analog element by the device of the invention. The invention has high sensitivity, little gas consumption, multiple detection components and strong anti-jamming capability, can effectively detect SF6, CF4, SO2F2, SOF2, SO2, HF and the like as low as 0.01 muL/L, and is suitable for on-line detection. The invention can be widely used for detection of partial discharge decomposed gas of SF6 in the SF6 gas insulating electrical equipment, especially the GIS equipment.