The flexure-based X-Y adjusting mechanism is applied in lithograph projection objectives to compensate the eccentric position of the optical elements in X-Y direction. Based on flexible hinges, two-stage flexible deceleration mechanism is designed. Further, making use of the two-stage flexible deceleration mechanism, a flexure-based X-Y adjusting mechanism which is new and of one part is created. Based on the analysis of the principle of the mechanism, structural parameters of the flexure-based X-Y adjusting mechanism are optimized. Moreover, using finite element method, performance of the flexure-based X-Y adjusting mechanism is studied. The results showed that the adjusting stroke is greater than ±20 μm, the displacement input-output relationship of the mechanism is steady, the transmission ratio is 11.9, the theoretically regulation accuracy is about 8.4 nm, the single-direction drive stiffness is 0.473 μm/N, and the ratio of coupling error and the main movement is 7.1%, when the mechanism moves open-loop and single-axis, and the first modal frequency is greater than 200 Hz. The flexure-based X-Y adjusting mechanism can be used in lithograph projection objective.