The present invention discloses a preparation method for nanometer platinum electrocatalyst which is used for direct methanol fuel cell, which belongs to the electrochemistry catalysis technology field. The preparation method comprises the steps of: adding stabilizer to platinic compound aqueous solution and controlling the pH value and the temperature of the solution; after stabilizing solution is formed, reducing under certain conditions to obtain unsupported catalyst. The catalyst of the present invention has a particle diameter of 2~5 nm, and has the advantages of that the size distributions centralized, the preparation method is simple, the operation is easy, the cost is low, and the present invention is adapted to industrial production. Single Cell Testing indicates that the catalyst has comparative properties with overseas like products.