Construction method for subway deep foundation pit adjacent to railway business line

The invention provides a construction method for a subway deep foundation pit adjacent to a railway business line. The construction method comprises the following steps that firstly, a foundation pit supporting structure is constructed; a supporting structure mainly adopted by the foundation pit body is formed by combining secant piles with inner supports to conduct foundation pit supporting and serve as a waterproof curtain. 2, foundation pit earthwork excavation construction is conducted, specifically, a foundation pit is excavated in a longitudinal segmentation and vertical layering mode, grooving supporting is conducted, supporting is conducted firstly, then excavation is conducted, and excavation is conducted while supporting is conducted; 3, a subway station main body structure is constructed, specifically, the subway station main body structure is constructed through an open excavation method, longitudinally segmented and vertically layered, and construction is conducted from bottom to top; and 4, afte