The invention provides a hydroxypropy rotaxane-phospholipid polymer. The polymer has a structural formula shown in the following formula (I), wherein n is 6, t is between 6 and 8, a is between 20 and 22, A is m, 14 or 16, and R is Y, q or between 40 and 91. The invention also provides a preparation method for the hydroxypropy rotaxane-phospholipid polymer, polymer nanoparticles and the application of the polymer nanoparticles when used as medicament carriers. The polymer nanoparticles have the advantages of high medicament loading rate, wide medicament loading range, high stability, long retention time in vivo, unique in-vivo distribution, increase of medicinal stability, improvement in bioavailability and reduction of side and toxic effects.