A hydrate kinetic inhibitor, which is prepared by a polymerization of mercaptoethanol and N-vinylcaprolactam, is hydroxyl terminated poly(N-vinylcaprolactam) having a structure of formula (I) below, wherein n=10 to 1000. The inhibitor is a novel hydrate kinetic inhibitor, which has low effective concentration and high cloud point, and is effective when the degree of supercooling is relatively high.