A process for producing ethylene and propylene from methanol and/or dimethyl ether, comprising the steps of: (a) contacting methanol and/or dimethyl ether with a catalyst, reacting to generate Hydrocarbons I; (b) separating said Hydrocarbons I obtained from step (a) into a C 1 -C 5 component from Hydrocarbons I and a C 6 + component from Hydrocarbons I; (c) mixing said C 6 + component from Hydrocarbons I obtained from step (b) with methanol and/or dimethyl ether to generate a mixture material, and contacting the mixture material with said catalyst, then allowing the mixture material to react and generate Hydrocarbons II; (d) separating said Hydrocarbons II obtained from step (c) into C 1 -C 5 component from Hydrocarbons II and a C 6 + component from Hydrocarbons II, both components containing ethylene and propylene, wherein said C 1 -C 5 component from Hydrocarbons II is collected as the target product and said C 6 + component from Hydrocarbons II is recycled to step (c); and (e) repeating step (c) and step (d), wherein a mixture material formed by mixing said C 6 + component from Hydrocarbons II obtained in step (d) with methanol and/or dimethyl ether is used in step (c), wherein the C 6 + component is recycled, and fed into a mixture with methanol and/or dimethyl ether to react, so that said C 1 -C 5 component from Hydrocarbons II containing ethylene and propylene is obtained continuously; wherein said catalyst is a molecular sieve catalyst co-modified by lanthanum and silicon, wherein said molecular sieve is HZSM-5 and/or HZSM-11 zeolite molecular sieve; wherein said catalyst co-modified by lanthanum and silicon is loaded by lanthanum, and its surface acidity is modified by silicon compounds; wherein the loading amount of said lanthanum is 0.5-5 wt% of the total weight of said catalyst, wherein the loading amount of said silicon compounds, which is based on silicon oxide, is 0.1-10 wt% of the total weight of said catalyst. (a) contacting methanol and/or dimethyl ether with a catalyst, reacting to generate Hydrocarbons I; (b) separating said Hydrocarbons I obtained from step (a) into a C 1 -C 5 component from Hydrocarbons I and a C 6 + component from Hydrocarbons I; (c) mixing said C 6 + component from Hydrocarbons I obtained from step (b) with methanol and/or dimethyl ether to generate a mixture material, and contacting the mixture material with said catalyst, then allowing the mixture material to react and generate Hydrocarbons II; (d) separating said Hydrocarbons II obtained from step (c) into C 1 -C 5 component from Hydrocarbons II and a C 6 + component from Hydrocarbons II, both components containing ethylene and propylene, wherein said C 1 -C 5 component from Hydrocarbons II is collected as the target product and said C 6 + component from Hydrocarbons II is recycled to step (c); and (e) repeating step (c) and step (d), wherein a mixture material formed by mixing said C 6 + component from Hydrocarbons II obtained in step (d) with methanol and/or dimethyl ether is used in step (c), wherein the C 6 + component is recycled, and fed into a mixture with methanol and/or dimethyl ether to react, so that said C 1 -C 5 component from Hydrocarbons II containing ethylene and propylene is obtained continuously;