A process for producing light olefins is provided. A feedstock enters a pre-reaction zone and contacts a catalyst comprising at least one silicon-aluminophosphate molecular sieve and produces a gas-phase stream; the gas-phase stream and the catalyst enter at least one riser, and the gas-phase stream and the catalyst pass from an outlet of the at least one riser and enter a gas-solid rapid separation zone; the separated gas-phase stream enters a separation section; a first portion of the separated catalyst returns to the pre-reaction zone, and a second portion is regenerated in a regenerator; wherein an inlet of the at least one riser extends into the pre-reaction zone, about 60% to about 90% of the height of the at least one riser passes through a heat exchange zone, and the outlet extends into the gas-solid rapid separation zone.