The dosimeter with the dose range suitable for the radiation processing is few. This paper describes the alanine free radical dosimeter by chemical read-out. The irradiation alanine (50 mg) are dissolved in 10 ml of the solution containing 0.20 mmol/1 ferrous sulphate and 0.20 mmol/1 xylenol orange in 0.025 mol/1 sulphuric acid (FX). The absorbance of ferric-xylenol orange complex in the presence of alanine is measured at 540nm—550nm. The dose ranged from 200 Gy to 10 kGy can be measured. The dosimeter is quite stable for about one year after the irradiation. The technique is simple and accurate. The results are very good.