The invention discloses a method for molding a green sand core of a T-shaped junction box, belonging to the method for casting and molding metal, in particular for molding a mold core of a hollow casting. The method for molding the green sand core of the T-shaped junction box improves the structure of a mould and adopts the structure that a bipartite core box chamber is arranged in a lower core box, thereby solving the problem of hard demoulding during the green sand core molding, achieving the purpose of using ordinary molding sand for producing the green sand core of the T-shaped junction box and improving the working efficiency; with the original method for molding the green sand core of the T-shaped junction box in the casting room of the company, only 80 boxes of green sand cores canbe produced by 4 workers each day, the rate of finished green sand cores is low, and the qualification rate of casted green sand cores is only 60 percent; while after the application of the method ofthe invention, 350 boxes of green sand cores can be produced by 3 workers each day, the working efficiency of the workers is increased nearly by 6 times, the rate of finished green sand cores is high, and the qualification rate of casted green sand cores is more than 90 percent. The method adopting resin bonded sand for producing the green sand core reduces the cost, and the method can be used for similar structural casting.