The application relates to the field of catalyst materials, and specifically discloses a preparation method of a highly stable methanol fuel decomposition catalyst. The following preparation steps are included: S1, adding copper nitrate, magnesium nitrate and aluminum nitrate to deionized water, stirring and mixing with sodium carbonate solution to obtain a matrix liquid; S2, adjusting the pH of the matrix liquid, standing for aging, and removing the lower layer of precipitation and crystallization treatment, heat preservation and roasting to obtain matrix particles; S3, by weight parts, respectively weigh 45-50 parts of solvent, 0.5-1.0 parts of modified graphite particles and 3-5 parts of chloroplatinic acid and stir and mix to obtain a reaction solution ; S4, hydrothermal treatment under argon atmosphere, adjust the pH to 2.5, filter and collect the precipitate, wash, dry, crush and sieve. The application firstly prepares the hydrotalcite substrate, and then composites the graphite surface loaded with reduced platinum simple substance with the hydrotalcite substrate, which improves the activity of the methanol decomposition catalyst in the catalytic decomposition reaction and improves the stability of the catalyst.