The invention discloses a movable platform using a gear and a rack for adjusting the width. The movable platform comprises a main trolley body, walking parts and a width adjusting device. The width adjusting device is connected with the main trolley body and the two walking parts and comprises a gear and rack mechanism and a driving unit; the gear and rack mechanism comprises a base, a gear and two rack connecting pieces, wherein the base is connected with the main trolley body, the gear is connected with the base in a pivoting mode, the two rack connecting pieces and the base form a moving pair, and the two rack connecting pieces are arranged at the two sides of the gear in parallel, meshed with the gear and connected with the two walking parts respectively; the driving unit drives the gear and rack mechanism to do meshing motion, and the two gear and rack connecting pieces drive the two walking parts to move oppositely at the same time to achieve space adjustment between the two walking parts. The invention further provides a robot with the movable platform using the gear and the rack for adjusting the width.