The invention discloses a spraying device for a SNCR (selective non-catalytic reduction) denitrifying system. The spraying device mainly consists of a first air pipe, a reductant pipe and a second air pipe, and is characterized in that the reductant pipe is sheathed on the first air pipe, and the second air pipe is sheathed on the reductant pipe; a first reductant passage and a second reductant passage are formed between the first air pipe and the reductant pipe, and a second compressed air passage is formed between the reductant pipe and the second air pipe. The spraying device has the advantages that the flowing-out potential energy of the reductant is increased by the vacuum suction force; after spraying and atomizing, secondary atomizing, and third atomizing, the liquid droplets of the reductant are more uniform and finer, and the denitrifying efficiency is improved.