The invention discloses a construction method for turnout loosening and locking in low temperature environment. The method comprises the following steps: (1) setting up a warm shed around a turnout; (2) loosening turnout fasteners and putting a roller under the turnout; (3) rising temperature of the warm shed; (4) adjusting temperature in the shed; (5) taking off the roller; (6) locking the turnout; (7) completing to weld steel rails on the front and rear of the turnout; (8) and removing the warm shed. Through setting up the warm shed around the turnout and arranging a hot-air blower in the warm shed, the turnout is heated, and a rubber hammer is used to knock the steel rails along all ranges of the steel rails to realize loosening in a temperature rising process, and when the temperature rises to designed stress-free temperature, the turnout is locked. The method realizes loosening and locking of a large-scale turnout in winter low temperature environment.