The invention discloses an indoor localization system for a mobile robot. The indoor localization system for the mobile robot, which improves localization accuracy, is designed on the basis of UWB (ultra wide band) technology combined with information of a motor encoder. A localization calculation method provided in the invention is a localization calculation method for the indoor mobile robot, and includes five steps: 1, confirming an origin of coordinates, starting a base station and the indoor mobile robot, and using a pose 2 of the indoor mobile robot, measured when starting the indoor mobile robot, as an initial pose; 2, obtaining an instant pose 1 of the mobile robot at moment t through the motor encoder; 3, receiving a high frequency electromagnetic pulse transmitted by the base station through a label, and confirming the self position of the mobile robot through a calculation method; 4, using a course angle measured by an electronic compass for augmenting the position of the mobile robot, obtained in the step 3, and obtaining an initial pose 2 at the moment t; 5, using the calculation method to fuse the initial pose 1 and the initial pose 2, obtaining pose estimation of the moment t, and saving the pose estimation and returning to the step 2.