The invention discloses a double-split starting method of a small-clearance double-line tunnel shield. The method comprises the following steps that arranging a starting station main body structure, backfilling and reinforcing a starting end, installing a temporary seal of a tunnel door, installing a starting frame, assembling and debugging a shield, installing a reaction frame, installing a negative ring segment, and performing starting trial tunneling of the shield. According to the method, the reasonable space layout is carried out on a starting station structure well, temporary reverse hidden excavation pilot tunnel is constructed to assist split starting, the shield starting frame, the reaction frame and the negative ring segment are sequentially installed, the split starting construction of the double-line small-clearance tunnel shield under the condition that the whole starting is difficult due to the insufficient space of a site is realized, and engineering practice verifies that the split starting method has the advantages of small construction cross influence, small influence on the surrounding environment, reduction of construction period pressure, safety, reliability and the like, and can be applicable to projects with insufficient length of the end well of the subway shield starting vehicle station.