In order to solve the problems of rapidly recognizing the shapes of the tumour in the stomach, a new kind of capsule endoscopy with through-body radar is utilized for the first time. Finite difference time domain method is used to establish an electromagnetic simulation model of stomach. After being swallowed by a patient, the capsule which consists of the radar moves through esophagus and stomach. Finally it drains out of the body by the self peristalsis of the human GI tract. During this time, the radar is used to transmit accurate radar data of human stomach. Then we will carry out electromagnetic inverse scattering imaging by back projection algorithm with the radar data. The algorithm must consider the influence of various tissues in the human body: the attenuation of the signal strength of electromagnetic waves, the decrease in speed and the refraction due to the different permittivities between the different organs of the body. These factors will eventually lead to image offset, and even generating a virtual image. It is effective to refrain the displacement of image with modifying the time element of the imaging algorithm by iteration. It is shown that ultra-wideband radar built-in capsule endoscopy can track and locate targets in the human's stomach.