目的　比较方根式、一维式和面积周长比 3种方法计算的电子束矩形照射野输出因子的精确性和可行性。方法　用电离室法对不同大小限光筒不同能量下 8个特定矩形照射野输出因子实测和用 3种方法计算 ,比较此 3种方法与实测值偏差。结果　 (1 )同一能量下 ,面积周长比法偏差较大 ,一维式和方根式偏差较小 ;(2 )电子束限光筒大小、射线能量和矩形照射野大小对 3种方法计算的矩形照射野输出因子有一定影响。结论　面积周长比法计算矩形照射野输出因子偏差较大 ,建议不予采用。一维式和方根式法精度较高 ,一维式法优于方根式法 ,而方根式法更适合于临床 OBJECTIVE To compare the accuracy and feasibility of the output factors of square beam radiation fields calculated by three methods: square root, one-dimensional and area perimeter. Methods The output factors of eight specific rectangular irradiation fields with different energy levels of different sizes were measured by ionization chamber method and calculated by three methods. The deviations of the three methods from the measured values ​​were compared. Results (1) Under the same energy, the perimeter of the area is larger than that of the method, and the deviation of the one-dimensional and square root is small. (2) The size of the beam, the energy of the beam and the size of the rectangular irradiation field are calculated for the three methods Rectangular radiation field output factor has a certain impact. Conclusion The area perimeter is larger than the method of calculating rectangular output field deviation factor, it is not recommended. The one-dimensional and square root methods have higher precision, one-dimensional method is better than the square root method, and the square root method is more suitable for clinical