CRD construction method for underground excavated tunnel in loess area to closely and underneath pass through existing station

The invention discloses a CRD construction method for a subsurface tunnel in a loess area to closely pass through an existing station, and relates to the technical field of tunnels. The construction method comprises the following steps that firstly, when a tunnel is excavated to the joint of a standard underground excavation section and a rectangular section, first-stage full-section WSS deep hole grouting is conducted; secondly, a left pilot tunnel of the tunnel is excavated, a pilot tunnel waterproof layer is laid on the left pilot tunnel, a secondary lining is poured, and after secondary lining concrete reaches the strength, a temporary steel support is erected; thirdly, after the left pilot tunnel is excavated, a right pilot tunnel is excavated in the second step; and 4, dismantling the temporary steel support according to the monitoring condition. According to the construction method, the construction sequence of the secondary lining is adjusted, settlement deformation of the existing station in the clos