The ground clutter of sidelooking Multiple-Input Multiple-Output (MIMO) bistatic radar has severe problems of range-dependence and clutter spectrum spreading. In this paper, the clutter characteristics of bistatic airborne radars are analyzed and a method of range-ambiguous clutter suppression is proposed. This method employs the range-dependent phase term in the traditional MIMO bistatic radar to provide extra degrees of freedom. The range information of the phase term enables clutter separation with different ranges and consequent suppression. Thus, a range-ambiguous clutter suppression for bistatic airborne early warning radars is achieved. The simulation results show the accuracy of the method. By a comparison with the existing Doppler Warping (DW) and clutter suppression method with the Improved Factor (IF) line, the results showed that the method has better performance, which proved the effectiveness of ambiguous clutter suppression in MIMO bistatic radars.