Poly(N-(2-hydroxypropyl) methacrylamide) (PHPMA), a water soluble polymer bearing a stable structure, can be metabolized in the human body. Because of that, PHPMA is widely used in anticancer drug’s delivery systems. The drug delivery systems based on the PHPMA have been extensively studied over the past few decades. Scientists use different kinds of functional groups to modify the polymer, which can deliver drugs to targeted tissue or detect pathogenic tissue. In recent studies, scientists enhance the degradability of the polymer and decrease the cytotoxicity, which makes the delivery system based on PHPMA more suitable to be utlized in human body. In this paper, we summarize the recent works about PHPMA and studies of different methods to modify the polymer with drugs or functional groups.