The present invention relates to the field of polypeptides, and particularly, provides a pharmaceutical composition and a manufacturing method thereof. The pharmaceutical composition comprises a Liraglutide, and the manufacturing method of the pharmaceutical composition comprises : mixing, in a solvent, the Liraglutide and an adjuvant, stirring the resultant mixture at 500-1100 rpm until homogeneous, and adjusting the pH value to 7.5-9.5. Various manufacturing process parameters can influence the stability of Liraglutide and may cause significant changes in oligomerization, single maximal impurity, and total impurity. The infrared spectra show an amide band I (at about 1645 nm -1 ), indicating the presence of an ?helix structure, with strong absorption and a basically consistent peak shape. The present invention controls, by examination of the secondary structure of a polypeptide, parameter screening of a pharmaceutical preparation process.