The invention discloses an efficient reburning denitrification device which comprises a decomposing furnace. The bottom of the decomposing furnace is provided with a secondary air inlet and is connected with a rotary cement kiln. The decomposing furnace comprises a main low-nitrogen burner and a reburning burner on the lower portion from bottom to top, and a raw material inlet is arranged at the position of the main low-nitrogen burner. Coal powder in a coal powder bunker enters the decomposing furnace from the main low-nitrogen burner and the reburning burner. A tertiary air inlet is arranged below the raw material inlet and connected with a cooler of the rotary cement kiln. The decomposing furnace comprises an overfire air inlet and an SNCR (selective non-catalytic reduction) spray gun on the upper portion from bottom to top. The overfire air inlet is connected with the tertiary air inlet and the cooler of the rotary cement kiln. The SNCR spray gun is connected with a centrifugal pump and an ammonia water storage tank device. A smoke outlet is arranged at the upper section of the decomposing furnace and connected with a cyclone preheater, an electric dust collector and a chimney. The invention further provides a technical reburning denitrification method by the efficient reburning denitrification device. By the efficient reburning denitrification device and the technical reburning denitrification method, NOx removal efficiency can be improved, sprayed ammonia water is reduced, and denitrification cost of cement enterprises is lowered.