Abstract: The paper introduces the spatial power-combining technique. According as a formula of the spatial power-combining is deduced by electromagnetism radiate theory, the main factors affecting the spatial power-combining efficiency is analyzed. According to characteristic of nanosecond narrow pulse, the factors affecting the combining efficiency is brought forward, then, a calculation of improving the spatial power efficiency of combining narrow pulse is put forward. Based on the deduction, an equipment of 16 channel nanosecond narrow pulse power combined in spatial is designed. The testing showers the combining efficiency about 81%. The fact accords with formula.