Synthetic aperture radar（SAR） imagery is one of the most advanced technologies in recent two decades in microwave remote sensing.As the resolution reaches a meter order

reconstruction of the 3D stereo objects on the terrain surface from all-weather SAR image becomes more feasible.Due to some technical limitations

conventional radar measurements are mostly restricted to classifying

inverting and reconstructing the stereo objects.It remains for further study via fully polarimetric SAR imagery with high resolution.Since pioneer experiments of SIR-C in 1994

some airborne and satellite-borne polarimetric SAR have been developed.The satellite-borne ALOS phase array polarimetric SAR at L band was launched in January 2006.Canadian Radarsat-2 polarimetric SAR at C band will be in orbit in 2007.How to effectively implement broad applications of polarimetric SAR images has become an extensive topic.The PI-SAR is a Japanese airborne polarimetric and interferometric SAR with two independent radar systems（L band-1.27 GHz

3m resolution

and X band-9.55GHz

1.5m resolution）.Interferometric data at X band and only polarimetric data at L band can be obtained.Fully polarimetric data from the square loop flights of PI-SAR over Sendai city

Japan in 2004 becomes available.Multi-directional flights can see the 3D objects in different angles and lead to reconstruction of those stereo objects.In this paper

the images of coherency matrix components derived from polarimetric PI-SAR images of two converse flights at X band

are employed which are mostly characterized by double bounce scattering between the building sides and ground surface

a feasible approach to reconstruct the 3D stereo objects

such as a TV tower and campus buildings is developed.Reconstructions of the building targets are validated by the real ground truth.