Abstract: The first brazed seam rate of braze welding which is the important craft link in manufacture process of model CANDU-6 nuclear fuel element will influence the stability of braze welding that follow up slope mouth processed and measurement, and the core agglomeration fills in complexity and end cap welding of the seal and the quality. So we should control the first brazed seam rate well and reduce the first unbrazed seam rate. The influence of the factors, such as the craft parameter, quality of the thickness of the beryllium coating and supporting cushion, etc. to the first brazed seam rate was explained, and the welding craft parameter, the thickness of beryllium coating and control range which supports the quality of the cushion through the experiment were confirmed. The purpose to control the first brazed seam rate was achieved.