Abstract: BESⅢ requires the matter mass of beryllium beam pipe is as few as possible, the heat on the inner wall of beryllium beam pipe must be taken away by cooling fluid, and the temperature on the outer wall must be controlled in the required range. In order to do this, the width of narrow annuli cooling channel of beryllium beam pipe was designed by optimization method, the theoretical analysis and finite element method were used, then the optimal width was chosen, the influence of concentrated heat on the temperature of inner and outer wall was studied, and the optimal working velocity of cooling fluid was given. The trim size experiment model of beam pipe was manufactured according to the designed structure. The experiment result shows that the designed cooling structure of beryllium beam pipe is reliable and the optimal velocity satisfies the requirement of cooling.