Chang, who was born in T'ai-yüan in China, was educated at the Tsinghua University in Peking, and at Cambridge, England, where he obtained his PhD in 1941. He emigrated to America in 1945 and joined the Worcester Foundation in Shrewsbury, Massachusetts, where he subsequently remained. From 1961 he also served as professor of reproductive biology at Boston University.

Chang carried out a number of major research projects from which emerged not only greater understanding of the mechanisms of mammalian fertilization, but also such practical consequences as oral contraceptives and the transplantation of human ova fertilized in vitro (by Robert Edwards and Patrick Steptoe in 1978). In 1951, at the same time as Colin Austin, Chang discovered that a “period of time in the female tract is required for the spermatozoa to acquire their fertilizing capacity,” a phenomenon known later as capacitation. He further demonstrated, in 1957, that there is a decapacitation factor in the seminal fluid, which, although it can be removed by centrifugation, has resisted further attempts at identification.

Chang also made the important advance in 1959 of fertilizing rabbit eggs in vitro and transplanting them into a recipient doe. This was followed in 1964 by comparable work for the first time with rodents. It was also Chang who provided much of the experimental basis for Gregory Pincus's 1953 paper showing that injections of progesterone into rabbits could serve as a contraceptive by inhibiting ovulation.