The invention belongs to the field of calculation, measurement and statistics, and particularly relates to a method for evaluating the uncertainty of a measuring result of a laser particle size analyzer. The method comprises the following steps that 1, three national particle standard substances different in particle size are selected and subjected to particle size analysis through the laser particle size analyzer; 2, statistics is carried out on various uncertainty components, namely, uncertainty U1 caused by an accidental error, uncertainty U2 caused by an instrument system error, uncertainty U3 introduced by the standard substances, and uncertainty U4 caused by layout of sensors in the laser particle size analyzer, influencing the measurement result; 3, uncertainty analysis is carried out. The scientific and standard method is provided for evaluation of the reliability of the measurement result of the laser particle size analyzer; laser particle size analyzers used by different users can be evaluated through the method so that the reliability of analysis results can be evaluated; meanwhile, the analysis results of different users have comparability.