Abstract: Gamma reference radiation produced by isotope sources ¹³⁷Cs and ⁶⁰Co is very necessary for calibration of radiation dosimeter. For the calibration of area monitoring dosimeter, reference radiation must provide the conventionally true value of the ambient dose equivalent H*(10). According to the recommendation given in the international standard ISO 4037-4, the conventionally true value of H*(10)could be obtained by two methods, one is spectrum method, the other is H*(10) standard ionization chamber methed. In order to establish a standard chamber which could meet the requirements of ISO4037-4, a design for H*(10) standard chamber was established by MCNP4C Monte Carlo simulation program. The results showed that the energy response of the ionization chamber satisfied the requirement of international standard ISO4037-4 from 15 keV to 1500 keV, the conclusion of this study was good to the establishment of H*(10) secondary standard ionization chamber.