A new computerized tomography (CT) technique based on differential optical absorption spectroscopy for the measurement of concentration field is proposed.A typical CT diagnoses system is designed，which consists of three parts: the lamp-house and its control system,the optical scanning measurement system and the data collecting and processing system,and numerical simulations are made.The results show that the projection data are obtained at only four viewing directions from range 0° to 180°,the maximum error of reconstruction image is less than 5％，and the average error is less than 1％.