Abstract: Otto Stern won the Nobel Prize in Physics in 1943 for the development of molecular beam methods

and the discovery of proton magnetic moments. In 1933，Stern and his collaborators measured proton magnetic moments.

The measurement of proton magnetic moments expanded the way for human to explore the micro world and

accelerated the process of people’s understanding of nuclear structure. The experiment of magnetic moment measurement

has been carried out and the whole process of proton magnetic moment measurement by Stern et al. has

been deeply excavated. The purpose is to clarify Stern’s pioneering contribution to proton magnetic moment measurement

and the contribution of the experiment to the development of nuclear physics in the 1930s.

Key words: proton magnetic moment, Otto Stern, molecular beam method