This research affords a new method to test the content of methanol in the gasoline, and a special portable instrument was developed according to this method. The disturbance caused by the existence of hydrocarbons and ethers in gasoline was excluded by extraction, and the alcohol was selective oxidized to aldehyde over catalyst A, and the presence of other alcohol can be neglected by selecting suitable color developing agent. The methanol content in 10 different kinds of gasoline samples (including samples of five Ethanol gasolines and of five unleaded gasoline) has been tested by this special instrument. According to the experimental data with GC and this method, the testing speed, selectivity and reliability of the method has been investigated, and the results shows that good reproducibility and accuracy of this method has been demonstrated as compared with those of other rapid test methods.