The present invention discloses a preparation method for 3,3,3-trifluoropropenyl methyl ether (CF3CH=CHOCH3). In the prior art, the reaction yield is low, the raw materials are difficult to be obtained, the cost is high. A purpose of the present invention is to solve the problems in the prior art. With the present invention, 1,2-dibromo-3,3,3-trifluoropropane is adopted as a raw material; the preparation method comprises the following steps: during stirring, adding methanol, an alkali to a reactor, then adding 1,2-dibromo-3,3,3-trifluoropropane, heating to a temperature of 70 DEG C, carrying out the reaction for 6 hours, wherein a mole ratio of the 1,2-dibromo-3,3,3-trifluoropropane to the methanol to the alkali is 1:3-8:2.4-6. The preparation method provided by the present invention is mainly applicable for preparing the 3,3,3-trifluoropropenyl methyl ether.