The invention discloses a construction method for additionally arranging a casing lining in a business line tunnel. The construction method specifically comprises the following steps that ditch cablegrooves are broken, micro-piles are applied, an existing lining is scabbled, a steel frame cover arch is erected, the ditch cable grooves are restored and concrete is sprayed; the concrete is preparedfrom the following components in parts: 450-480 parts of cement, 800-820 parts of coarse aggregate, 900-920 parts of fine aggregate, 4-5 parts of a water reducer and 160-180 parts of water, an accelerator is added during spraying, and the adding dosage of the accelerator is not more than 4% of the weight of the cement. According to the technical scheme, the casing lining is additionally arrangedin the business line tunnel through a concrete spraying method, work procedures such as template installing, pouring and tamping through a moulding method are not needed, construction is fast and easy, the concrete strength loss is small after construction, and thus the operation safety of the business line tunnel is effectively improved.