Abstract: Aiming at the machining errors arising during the rough machining of tenons of thin-walled steam turbine blades after forging, which induce deviations in the clamping datum of subsequent machine tools, a set of flexible adaptive fixtures was designed based on the SMU800 five-axis blade machining center. The fixture adopted a clamping design of "one end fixed, one end floating" and was equipped with an end-face floating jacking function to compensate for tenon size deviations. Ansys analysis of martensitic stainless steel steam turbine blades showed that the deformation under vertical clamping orientation was reduced by 0.003 mm compared to the horizontal posture. Under a floating jacking oil pressure of 1 MPa (corresponding to a jacking force of approximately 410 N), the workpiece deformation in the vertical posture was 0.005 mm. Finite element validation and modal analysis of key fixture components indicated that the maximum stress on the lever under the designed clamping force of 33 kN was 233.64 MPa, which was far below the maximum allowable stress. The natural frequency of the machine tool was found to be 1 886.7 Hz, effectively avoiding spindle resonance. This research provides an effective solution for improving the five-axis machining accuracy of thin-walled blades.