The invention relates to a low-temperature dry distillation process for coal, in particular to a high-efficiency lignite low-temperature dry distillation quality-enhancing process by using dry distillation coal gas as a heat-carrying medium. The process comprises a coal-preparing flow, a drying flow, a dry distillation flow, a heat source flow, a coal gas and tar processing flow and a semicoke cooling transfer flow; in the process, vapor self-generated by a drying tower is used as a drying medium, the coal gas of a generator is taken as a heat source to heat the self-generated dry distillation coal gas, and serves as a dry distillation medium, and the coal gas of the generator is used as fuel of a hot air furnace; the dry distillation semicoke is cooled in a cooling mode of drying fume exhaust plus semi water spraying; and condensation water is used for coke-quenching water, a gasifier of the coal gas of the generator and a tar cooling agent. The process has the advantages of producing high-index dry coal and dry semicoke, high-heating value coal gas and high-quality tar, having a flawless and high-efficiency energy recycling system, not using outside nature water, hardly discharging water to the outside, saving huge cost for sewage treatment, creating the maximum economic benefits for customers and having quite strong competitive power on economy, technology and market.