A method for determining the hexagonal polytypes of silicon carbide using the Laue pattern is described. By the detailed studies on reciprocal lattice points of various hexagonal types xH of silicon carbide which are coalescent with 6H, 15R or 4H, the relations of the arrangement of their diffraction points has been derived. It is proved that there are twelve kinds of relation for the coalescence of xH with 6H, thirty for xH with 15R and eight for xH with 4H. The relations and the formulas which are given in this paper for the calculation of the numbers of hexagonal packed layers in unit cell of xH may be applied not only to the Laue technique but also to other x-ray techniques.A great number of single crystals of silicon carbide grown in laboratory by the sublimating procedure and of technical silicon carbide had been studied. Seven new hexagonal types 141H, 80H, 58H, 55H, 15H, 9H and 7H were found. The space group of all these new polytypes was determined to be C3m, and their lattice parameters c in the hexagonal cell are 355.26?, 201.57?, 146.14?, 138.58?, 37.794?, 22.676? and 17.637? respectively.