The decomposition mechanisms of a perfluoropolyether (ZDOL) at the head/disk interface under sliding friction conditions were studied using an ultra‐high vacuum tribometer equipped with a mass spectrometer. Chemical bonding theory was applied to analyze the decomposition process. For a carbon coated slider/CNx disk interface, the primary decomposed fragments are CFO and CF2O, caused by the friction decomposition and electron bombardment in the mass spectrometer. For an uncoated Al2O3–TiC slider/CNx contact, CF3 and C2F3 fragments appear in addition to CFO and CF2O, resulting from the catalytic reactions and friction decomposition, indicating that the decomposition mechanism associated with friction leads to the breaking of the main chain of ZDOL and forms CF2=O, which reacts with Al2O3 to produce AlF3, and the rapid catalytic decomposition of ZDOL on the AlF3 surface follows. Moreover, the effects of frictional heat, tribocharge, mechanical scission and Lewis acid catalytic action, generated in friction process, on the decomposition of ZDOL are discussed.