By changing the width L of stagger BTA middle tooth chip breaker, the problem of middle tooth breaker was researched. With the cutting speed of 62.8 m/min and feed rate of 0.2 mm/r,three stagger BTA ,whose middle tooth chip-breaker width were different,were used to drill the 45 steel.Through the analysis of cutting force and chip, the conclusion is obtained that the width L of stagger BTA middle tooth chip-breaker has impacts on middle tooth breaker.