Abstract: Potassium (sodium) fluosilicate scaling in pipes of filter is the main operation problem in the wet-process phosphoric acid (WPA) production from phosphate ore with high potassium and sodium content.At present there is no effective way to solve this problem because of lack of theoretical research. In this work, pipe flow experiment of supersaturated phosphoric acid solutions of potassium (sodium) fluosilicate was used to study scaling process on the pipe wall by simulating the vacuum filter cooling system in WPA production. As regards scale model, a fairly comprehensive population balance equation was used for the solid phase and a mass balance equation was used for the scaled ions. Heterogeneous nucleation and subsequent crystal growth right onto the pipe wall would lead to scale formation. A sufficiently accurate discretization scheme was used in the simulation algorithm. The scaling rate, scaling amount and particle size distributions were predicted with the model, and the results indicated that the predictions agreed well with the experimented data. The proposed model is a useful tool for scale up in practical WPA production and other scaling problem of similar systems.