The invention relates to a construction method for a newly-built subway tunnel to pass through an existing bridge pile. The method includes the following steps that when the subway tunnel is constructed in front of the existing bridge pile, full-cross-section grouting reinforcement is carried out on soil in front of the subway tunnel; the area of one side, away from the existing bridge pile, of the subway tunnel is constructed with a center cross diaphragm method to form a first pilot tunnel; after the first pilot tunnel runs through the existing bridge pile, the first pilot tunnel continues to be constructed forwards, the cross section of the first pilot tunnel is gradually changed into the cross section of the subway tunnel, and then the subway tunnel continues to be constructed forwards; pile foundation underpinning construction is carried out on the existing bridge pile; and after the pile foundation underpinning construction is completed, soil at the existing bridge pile is excavated to from a second pilot tunnel communicating with the first pilot tunnel, and the existing bridge pile in the second pilot tunnel is exploded away. By adopting an around-pile construction method, the synchronous construction of the subway tunnel and pile foundation underpinning of the existing bridge pile can be realized, the construction progress is accelerated, and the cost is saved.