The invention discloses an axial center alignment method for a steam turbine, and the method comprises the following steps: S1, collecting circumference values and end face values of all pair wheels; S2, importing axial design data; S3, designing an axial center alignment calculation interface; S4, enabling an output region with an input region and an adjustment region to be correlated through a computational formula, and enabling a conclusion region to be used for listing logic relations of openings and circumferences of all pair wheels with all pair wheel values corresponding to the output region; S5, adjusting a bearing bush value in the adjustment region so as to eliminate an axial center error; S6, recording the adjustment values of all bearing bushes when the axial center error is less than an axial center error critical value; S7, adjusting all bearing bushes according to the recorded adjustment values of all bearing bushes, thereby completing the axial center alignment. The method builds a new axial center alignment platform to improve the axial alignment efficiency through employing axial center alignment calculation software, greatly saves the labor and time, is high in efficiency, and is quick and convenient.