A spin annular slit spray nozzle includes: a core seat, a spin core, and a spin annular slit orifice. Said core seat has a core chamber, an inlet and an outlet communicated with the core chamber are provided on the core seat; the inlet of the core seat is communicated with a pressurized flow source; said spin core is limited in the core chamber which is concentric with the spin core and may rotate with respect to each other; spin-actuating channels are formed on the spin core or on the core chamber wall. Due to the spin power from the spin-actuating channels, the spin core and the core chamber can rotate with respect to each other; a core head on the outer end of the spin core extends into the outlet of the core chamber; the spin annular slit orifice is form between the core head and the outlet end of the core chamber; the cross-section of the orifice is nearly a circular ring; the fineness and the flow of the pressurized mist of the spray nozzle are controlled respectively through adjusting the gap and diameter of the ring, and the distribution of the drop sizes is thus uniformly finer. A spray apparatus comprises said spin annular slit spray nozzle and the sprinkler body communicated with the spray nozzle core seat.