Abstract: OBJECTIVE To investigate the polymorphism of felodipine solvatomorph systematically. METHODS A dimethyl sulfoxide solvate(1∶1) of felodipine, named form XIB, was prepared by crystallization from solvent through slow evaporation and characterized by X-ray crystallography, thermal analysis and Fourier transform infrared spectroscopy. RESULTS Compared with the reported form XIA, another felodipine dimethyl sulfoxide solvate(1∶1), found that the prepared sample was a new felodipine dimethyl sulfoxide solvate hypotype. Single-crystal X-ray diffraction results displayed that form XIB belonged to monoclinic P2_1/c space group, the unit cell consisted of four felodipine molecules and four dimethyl sulfoxide solvent molecules, respectively, and the host molecules interacted with the guest solvent molecules by hydrogen bond N-H…O. Differential scanning calorimetry and thermal gravimetric analyzer results also illustrated form XIB was a felodipine dimethyl sulfoxide solvate(1∶1). CONCLUSION It is revealed that felodipine dimethyl sulfoxide solvate(1:1) existed the polymorphism, including forms XIA and XIB. The molecular arrangements of forms XIA and XIB were obvious different as well as their simulated powder X-ray diffraction patterns.