As a key part of Hard Disc（HDI），the thin film of lube is possibly degraded and destroyed by the interaction between the magnetic head and disk during the hard disk working. Both TGA and FTIR are used to study lubes failure mechanism of HDI and investigate the function of X-1P as an additive in HDI lube. TGA experiment results show that the sample PFPE / X-1P / Al2O3 is much more stable than the sample PFPE / Al2O3 just as sample PFPE，and the sample PFPE / Al2O3 will degrade with high speed at enough high temperature. FTIR experiments present the results similar to that of TGA experiments. From IR sorption spectra at different heating times for the three samples，it can be found that the sample PFPE & the sample PFPE / X-1P / Al2O3 are similarly stable，but different from the sample PFPE / Al2O3 for which new CF = O absorption peak appeared after heated for 15 min and became stronger with the extending for heating time. FTIR experiment results further verifies that alumina is a catalyst for PFPE degradation reaction and X-1P can effectively passivate the catalyst and stabilize PFPE. In order to investigate X-1P's role to mechanical & tribological performances of HDI，the CSS experiment is also performed and the experiment results tell that the presence of X-1P dip-coated on the magnetic head can greatly reduce the friction between head and disk and improve CSS performance of HDI. In addition，the failure mechanism of HDI lube and X-1P's working principle as a HDI lube additive are analyzed and discussed respectively. The aluminum atom of alumina has empty orbits which can accept isolated electron pairs，and is a kind of Lewis acid with stronger electrophilic trend. Oxygen atom of PFPE has isolated electron pairs and shows nucleophilic trend. When the magnetic head contacts with the HDI lube，it is possible for alumina to induce PFPE to disproportionally degrade first from the ether bonding at enough high moment temperature. For X-1P，owing to its special molecule structure，not only has a good chemical stability but also shows stronger nucleophilic trend. When alumina contacts with the compounds of X-1P and PFPE，X-1P can be absorbed on the alumina surface prior to PFPE and keeps PFPE out of contact with alumina，and as such to protect PFPE out of degradation.