Synthesis of coarse-grain diamond crystals is studied in a China-type SPD6×1670T cubic high-pressure apparatus with high exact control system. To synthesize high quality coarse-gain diamond crystals, advanced indirect heat assembly, powder catalyst technology and optimized synthesis craft are used. At last, three kinds of coarse-grain diamond (about 0.85 mm) single crystals with hexahedron, hex-octahedron and octahedron are synthesized successfully under HPHT (about 5.4 GPa, 1300-1450℃). The growth characters of different shape crystals are discussed. The results and techniques might be useful for the production of coarse-grain diamonds.