Objective:To analyze three different kinds of finger shape ionization chamber of medical linear accelerator is used the response of the dose rate.Methods:Choose three different kinds of finger shape ionization chamber,they are respectively 0.6 cm3 PTW ionization chamber and 0.125 cm3 ionization chamber,IBA 0.01 cm3 of ionization chamber,accelerator in 100-600 cGy/min,within the limits of dose rate under the same measurement conditions and MU,respectively measuring and analysis of three different kinds of ionization chamber under the different working voltage and energy of the dose rate response characteristics.Results:Dosimeter working voltage and X ray energy are constantly,three kinds of ionization chamber of collection efficiency with the increase of the dose rate have a certain degree of lower,for the 6 mv X-ray energy,three kinds of ionization chamber corresponding to the maximum dose meter readings was reduced by 1.90%,2.51%and 1.90%,respectively,for 15 mv X-ray energy,the three largest ionization chamber was reduced by 3.60%,3.57%and 3.60%respectively; When dose rate must be collection efficiency with the increase of the working voltage and a certain degree of rise,when the working voltage higher collection efficiency is relatively stable.Conclusion:Different finger type of ionization chamber,the working voltage of dosimeter and dose rate change will have a certain influence on collection efficiency,In the clinical application of dose measurement on the linear accelerator,Need to test and analysis dose rate corresponding and the measuring equipment to ensure the accuracy of routine calibration and dose verification.