The invention relates to a method and device for determining a construction space of a heat-engine plant on the basis of a PM2.5 forming contribution rate. The method comprises the following steps: obtaining a reference year polluted atmosphere discharge amount and a target year polluted atmosphere discharge amount of a preset type of an atmosphere pollution source; respectively obtaining a reference year high-temporal-spatial resoluted atmosphere discharge list and a target year high-temporal-spatial resoluted atmosphere discharge list; respectively inputting the reference year high-temporal-spatial resoluted atmosphere discharge list and the target year high-temporal-spatial resoluted atmosphere discharge list into an air quality model to obtain contribution from the heat-engine plant to the concentration of the PM2.5 in the reference year and contribution from the heat-engine plant to the concentration of the PM2.5 in the target year; and when the contribution from the heat-engine plant to the concentration of the PM2.5 in the target year is less than the contribution from the heat-engine plant to the concentration of the PM2.5 in the reference year, determining that the construction space of the heat-engine plant exists in the target year. According to the method for determining the construction space of the heat-engine plant, the rate of contribution from the heat-engine plant to the concentration of the PM2.5 is fully considered, and the method can be used for determining whether the heat-engine plant has the construction space or not on the basis of the rate of contribution to the concentration of the PM2.5.