High power xenon flashlamp is mainly used in inertial confinement fusion (ICF) research as optical pump source for solid-state lasers. Its working performance and life time greatly influence the operation of lasers. A high power xenon flashlamp with relative small-bore and large arc-length is manufactured based on the development of tube material and wall structure. Two specifications are researched: one is diameter of 16 mm and arc-length of 1140 mm; the other is diameter of 17 mm and arc-length 1270 mm. The flashlamp has higher radiation efficiency compared with previous flashlamps. High explosive energy and satisfactory life time ensure its large output energy and good working stability.