The invention discloses two-section preparation process of propylene. Methanol and refinery carbon teterolefin are used as raw materials, water is used as a diluent, and a two-section fixed bed reactor is adopted for preparation. Catalyst in the first section of the fixed bed reactor contains 50%-85% ZSM-5 molecular sieve, and catalyst in the second section of the fixed bed reactor is magnesium element modified ZSM-5 molecular sieve catalyst. By means of the two-section preparation process of the propylene, water amount in the diluent is reduced, operation temperature is reduced, propylene selectivity and P/E ratio are effectively improved, conversion rate of the raw material methanol can reach as high as 100%, conversion rate of the refinery carbon teterolefin can reach above 85%, and one-way selectivity of propylene can reach as high as 50%.