The invention provides a positioning device and positioning method for pre-embedded bolt casting. The positioning device for pre-embedded bolt casting comprises a frame body and a screw fixing frame.The frame body comprises a square frame body and a specification adjusting rod. The two ends of the specification adjusting rod are in sliding connection with the square frame body through sliding controlling plugs. The screw fixing frame comprises a semicircular screw fixing and locking piece and a sliding fixing buckle. The screw fixing and locking piece is in sliding connection with the specification adjusting rod through the sliding fixing buckle. The positioning device for pre-embedded bolt casting is good in corrosion resistance and long in service life; through a transmission mechanismand detachable design, the labor intensity is reduced, operation is easy, adjusting is convenient, the stability and accuracy of a system are high, and the maintenance cost is low; and the process ofmanual continuous correction of a bolt position is omitted, the rework loss caused by bolt deviation is avoided, the blank that there is no positioning device in screw construction of a transformer substation is compensated, and the difficult problem that three-dimensional coordinates of transverse, vertical and elevation in the bolt pouring process are difficult to position is solved.