The invention discloses a soft measurement method of a coal slurry flotation cleans ash based on date-driven, which establishes a hardware platform and a flotation cleans ash. Flotation feeding concentration, flow, flotation medicament dosage and tailings flashboard position are used as auxiliary variables, the flotation cleans ash is used as a master variable, the auxiliary variables are used as input and the flotation cleans ash is used as model output so as to carry out soft measurement modeling, and calibration and parameter correction are carried out to a model so as to estimate the ash content of the current flotation cleans in real-time. The method has simple application and low cost, can realize the soft measurement of the flotation cleans ash by only needing a small quantity of samples, thus improving the measurement timelessness, and being beneficial to realizing the optimized control of the flotation procedure.