The invention discloses a thick fog prediction method, device and system, and belongs to the traffic meteorology early warning technical field; the method comprises the following steps: obtaining roadside meteorology data collected on at least three time points in a first time period, wherein the meteorology data comprises visibility data and/or atmospheric temperature data; determining whether the meteorology data has fluctuations or not in the first time period according to the obtained meteorology data; if yes, predicting thick fog formation in a second preset time period, wherein the predicted thick fog has the visibility smaller than a preset visibility value. The method, device and system can improve the thick fog prediction accuracy, and are applied to roadside thick fog predictions.