A solder spray jig includes: a main body having an opening acting as a spray outlet for solder, and recesses formed on two opposite sides of the main body and communicating with the spray outlet; a movable unit disposed on each of the two opposite sides of the main body, for covering and exposing a corresponding one of the recesses; and a driving device mounted to the movable units, for allowing the movable units to be operationally associated with each other to cover and expose the recesses. The spray outlet of the main body can keep abutting against a mold that covers a circuit board having electronic components when the main body is being moved horizontally in relation to the mold, so as to spray the solder via the spray outlet to effectively fix the electronic components to the circuit board.