It is well established that Synthetic Aperture Radar ( SAR) Interferometry can be used to perform surface elevation mapping and change detection. Among the factors critical to the mapping and detection accuracy is t he registration of the INSAR complex images from repeated orbits. This paper pre sents a method for registering INSAR complex images and two methods for interfer o gram enhancement. When registering complex images, area based registration metho d is used and the correlation coefficient between the corresponding data windows of the complex images is selected to evaluate the registration precision. With the method developed in this paper the INSAR complex images can be co-registered with the precision of sub-pixel. An interferogram can be obtained from the co-r egistered images. To reduce the noise of the interferogram median filter and dir ectional filter were experienced. The advantage of these filters is that the abu n dant fringe information of the interferogram is saved when smoothing the noise. These data processing methods have been applied to the SIR-C/X-SAR L band interf e rometric data of the Karakax area in the western China, and valuable results hav e been obtained.