There have hand-held GPR systems and vehicle-mounted GPR systems, which are offset from the air-ground interface by a nonnegligible distance, developed for landmine detection. Vehicle-mounted systems have exclusive advantage that can show subsurface imaging in horizontal slices based on grid GPR data set. Hand-held GPR system is one of advantageous technologies in mountain district etc. But hand-held GPR system usually cannot display subsurface imaging in horizontal slices because human being operator cannot precisely control GPR sensor to scan the measurement area along the regular survey line and observation positions are random. For both hand-held GPR systems and vehicle-mounted GPR systems, clutter reduction is very challenging due to these physical limitations. We used the technique of CMP antenna array and migration processing to improve the imaging quality for vehicle-mounted GPR systems, and used the modified migration algorithm to perform both interpolation and migration for hand-held GPR systems.