The crystal structure of alkaloide, koumine Hydrobromide (C20H22N2O·HBr), has been solved by Patterson and Fourier methods and refined to an R value of 0.067 by full-matrix least-square method. The crystal belongs to orthorhombic system with the unit cell parameters: a = 14.307?, b = 12.053?, c = 9.862?; and four molecules are contained in the cell. The space group is P21 21 21. The positions of all hydrogen acoms have been found from a difference Fourier map calculated after the refinement of co-ordinates of all non-hydrogen atoms with anisotropic thermal parameters by least-squares method. The absolute configuration of the molecule has been established. The structural characteristics of the molecule were discussed.