Abstract: A SIR-A image in the south of Tianjin acquired by the Shuttle Imaging Radar in November 1981 was interpreted directly and processed by computer system. The methods of processing were density slicing with statistical training; producing the normalized false color composite image through coregistration of the SIR-A and Landsat MSS data sets; unsupervised cluster classifications of some different image results of combining the Landsat MSS data and the SIR-A data. The interpretation keys using the SIR-A original image, the SIR-A density clicing image and the SIR-A/Landsat MSS normalized composite image to investigate land use situation were established after investigation in situ and analysis of the dielectric characteristics of different ground cover types and using large scale color IR aerial photo and land use maps aquired recently as the references, According to the keys an experiment on the aformentioned images interpretation and the interpretation accuracy analysis was undertaken. The results of the research indicate that the SIR-A data have higher resolution than Landsat MSS and remedy some defects of Landsat MSS data because of showing residential areas and linear features clearly, The SIRA/Landsat MSS normalized composite images incorporate the strong points of SIR-A and Landsat MSS data, have the resolution of the SIR-A image,reflect the ground surface spectral reflectance characteristics in the bands of visible and near infrared and the ground surface backscatter characteristics in the band of microwave and increase the classification accuracy that use remotely sensed data acquired by spacecrafts to land use maping.