High-quality type-Ib tower-shape diamond single crystals were synthesized in cubic anvil high pressure apparatus (SPD-6×1200) at 5.4 GPa and 1250-1450°C. The (100) face of seed crystal was used as the growth face, and FeNiMnCo alloy was used as the solvent/catalyst. Two kinds of carbon diffusing fields (type-B and type-G) were simulated by finite element method (FEM). Using the two kinds of carbon diffusing fields, many diamond single crystals were synthesized. The effects of carbon diffusing fields on the crystal quality and β value (the ratio of height to diameter of diamond crystal) were studied. The results show that using type-B diffusing field, considerable inclusions appeared in tower-shape diamond crystals with high β values; however, using type- G diffusing field, inclusions were reduced markedly in high β values tower-shape diamond crystals, and the crystal, up to 0.6 carat in weight and 5.3 mm in size, was synthesized. Experimental phenomena were explained well with the help of the FEM. High-quality type-Ib tower-shape diamond single crystals were synthesized in cubic anvil high pressure apparatus (SPD-6 × 1200) at 5.4 GPa and 1250-1450 ° C. The (100) face of seed crystal was used as the growth Two kinds of carbon diffusing fields (type-B and type-G) were simulated by finite element method (FEM). Using the two kinds of carbon diffusing fields, many diamond single The effects of carbon diffusing fields on the crystal quality and β value (the ratio of height to diameter of diamond crystal) were studied. The results show that using type-B diffusing field, extensive inclusions appeared in tower-shape diamond crystals with high β values; however, using type-G diffusing field, inclusions were reduced markedly in high β values ​​tower-shape diamond crystals, and the crystal, up to 0.6 carat in weight and 5.3 mm in size, was synthesized. were explained well with the help of the FEM.