The invention provides a die for constructing an urban mass transit turnout point switch foundation pit. The die comprises a point switch host foundation pit die block part and a rail penetrating groove die block part. The point switch host foundation pit die block part comprises six point switch host foundation pit die blocks with the same size. The rail penetrating groove die block part comprises middle rail penetrating groove die blocks and rail penetrating groove die blocks on the two sides. The point switch host foundation pit die block part and the rail penetrating groove die block part are spliced. The invention further provides a construction method of the die for constructing the urban mass transit turnout point switch foundation pit. The die and the method have the beneficial effects that the die with the uniform standard dimensions is utilized for launching the foundation pit construction project, the construction efficiency is improved, and meanwhile the labor cost of manual work is reduced; meanwhile, the reserving precision of the turnout point switch foundation pit is improved through the die, and the deviation of an original method for constructing the foundation pit is reduced to 10 mm from 50 mm; and the time of one day can be saved when each foundation pit is conducted, and the construction progress can be effectively promoted.