Inhomogeneous breast tissue has a strong scattering effect when the breast is illuminated by a detecting signal. This effect influences the tumor's response signal and makes the imaging result worse. This paper presents an efficient imaging approach to detect breast tumor in inhomogeneous tissue. We separated the transmitter and receiver to lower the rigorous request for antenna design. An ultra wideband microwave pulse was transmitted into the breast and the backscatter signal was received by each antenna in an array. The transmitter was set at four different locations sequently and four-group backscatter data were received and added together as the response signal from the tumor. Results of signal processing demonstrate that this method is superior to the previous methods and can localize the tumor efficiently.