A method was proposed of opening a circular arc groove at the bottom of the crystallizer to improve the uniformity of microstructure and composition of the horizontal continuous casting Cu-15 Ni-8 Sn alloy.Firstly,based on the temperature field simulation of horizontal continuous casting process of the alloy,influence of crystallizer structure with different arc groove angle,length and thickness was analyzed on temperature distribution in crystallization zone.Then,based on the optimized circular arc groove crystallizer and the crystallizer without the circular arc groove,a horizontal continuous casting process for a 65 mm diameter ingot was carried out.The results reveal that with the increase of the angle,length and thicknessof circular arc groove,the relative horizontal distance of the upper and lower solid-liquid interface is decreased,and the axial angle between the solid-liquid interface and the bar is tended to be 90°.Meanwhile,the temperature field uniformity of the billet is improved obviously during solidification.When the slot angle is 180°,the slot length is 144 mm and the slot thickness is 5 mm for the circular groove,the relative horizontal distance between the upper and lower solid-liquid interfaces is only7%to that without the circular groove.Due to the more reasonable temperature distribution,the uniformity of the microstructure and composition of the horizontal continuous casting Cu-15 Ni-8 Sn ingot is improved greatly.