Based on the research conclusions on the suitable meteorological conditions for Marathon races at home and abroad,the impact of weather factors on athletes'performance,and the meteorological disaster risk of sports e-vents,the scoring method and calculation formula of meteorological index for marathon races were designed.More-over,an index forecasting method was constructed by the characteristic element classification,interval threshold set-ting,and index level division.The results indicate that the main characteristic elements affecting Marathon races are temperature,precipitation,wind speed,humidity,air pressure,sunshine,ultraviolet radiation,air pollution,and se-vere convective weather.The calculated index level can reflect the impact of meteorological conditions on the races and the primary influencing meteorological conditions.When the meteorological index for Marathon races is level 1,the weather conditions are most suitable for the races;when the index is 2~3,there may be some adverse weath-er conditions that have a certain impact on the races;when the index is 4~5,there may be adverse weather condi-tions that have a high impact on the races;when the index is level 6,there may be disastrous weather conditions that have a serious impact on the races.The forecasting method of meteorological index for Marathon races can provide better meteorological service by"directly reflecting the suitability of meteorological conditions",thereby effectively improve the professionalism and pertinence of meteorological support services for the races.