Range-dependent clutter suppression is one of the most important problem in the airborne bistatic radar Space-Time Adaptive Processing (STAP). To overcome the problem, a novel technique using overlapped subarray alternate transmitting is developed. By virtue of the alternate transmitting, the clutter ridges of all range bins of airborne bistatic sidelooking radar are located in the same plane of a three-dimensional space which is constructed by transmitting spatial frequency, receiving frequency and Doppler frequency. Due to the range-independence of the clutter plane, it can be well suppressed by STAP. Then range-dependent clutter is efficiently suppressed. Numerical examples are given to demonstrate the effectiveness of the presented method.