Abstract: This paper discusses several aspects of theories on SAR interferometry.The different mathematic models of interferometry have been discussed and analysed.The paper points out that the ground coordinate system should be chosen carefully in case of using the mathematic model suggested by C.Prati et al and the tangent plane coordinate system must be taken into account.The model proposed by Ph.Hartl et al can be used without considering the earth curveture,but the calculations of base line and the incident angle for every point are the key factors and difficult to be done.The model by R.Gens et al is different in the conception of phase difference which is for one point only,not the difference of phase difference of two neighboring points.The paper aslo points out that the problems mentioned above should be taken into the consideration for applications.A mathematic model for elevation calculation has been proposed based upon the phase difference of two neighbor points to same antenna,and precise control point as the "seed",without taking into account the base-line assessment.The adjustments for the image coordinates of control points and satellite position parameters according to the imaging equations have also been suggest-ed in order to meet the needs of the precision of control points and satellite position for phase unwrapping and elevation calculation,as well as the method of base-line assessment.