The invention discloses a positioning system for a pre-embedded anchor bar of an arch support and a construction method applying the system and relates to the field of bridge construction. The system comprises a positioning support, an anchor bar positioning box, an accurate adjustment device and a chain block. According to the construction method for positioning of the pre-embedded anchor bar of the arch support, the engineering schedule is fast, the construction procedure is simple, the construction is safe and the accuracy is high; with the adoption of the positioning system for the pre-embedded anchor bar of the arch support, the cost input is low, the material consumption is small, the mounting is rapid, anchor bars are not required to be adjusted one by one, and anchor bar embedding in the complicated environment can be rapidly performed.