Abstract: 常咯啉 is an antiarrhythmic drug with a new chemical structure formula synthesized by Institute of Medicine, Academia Sinica. The chemical formula is C₂₄H₂₉O₁N₅. It is a fiat pale yellow crystal. The crystal was investigated using Philips PW1100 model single-crystal four-circle diffractometer. The lattice parameters obtained are as follows:_a=21.94Å, _b=5.90Å, _c=12.97Å,β=99.60°.It belongs to the monoclinic system with a space group P2₁/c.