Pyrimorph and its phenyl analog were prepared by chemical synthesis and their fungicidal activities were tested against P. infestans and P. capsici.We analyzed the structure of pyrimorph by X-ray diffraction method. Furthermore, the structure of pyrimorph and its phenyl analog were optimized by density functional theory using the 6-31G(2df, 2pd) basis set. Based on the calculated frontier molecular orbitals, Mulliken charges, natural bond orbital (NBO) analysis and surface electrostatic potential, the structure-activity relationships (SARs) of pyrimorph and its phenyl analog were discussed. The results show that when the phenyl ring is replaced by pyridine, hydrogen bond formation with a receptor molecule is favored due to the negative charge center of N in the pyridine ring. In addition, pyridine makes the electron-deficient aryl ring a better electron acceptor for π-πstacking. Considering the two above-mentioned factors, pyrimorph was found to bind more easily with the receptor and possessed better activity than its phenyl analog.