Objective To investigate the structure and scaling prevention properties of electroless Ni-Mo-P alloy coatings prepared in different deposition process conditions using the materials testing and scale experiment. Methods Under different processing conditions, by adding the heteropolyacid salt containing molybdate ion, the Ni-Mo-P alloy coatings were prepared by chemical deposition on the substrate which was firstly chemically deposited with Ni-P coatings. The surface morphology and structure of the electroless Ni-Mo-P alloy coatings were studied, the effects of the molybdate content and the boric acid content in the plating bath on the coating deposition rate were analyzed, and the surface morphology of the coatings was observed and the scaling rate was analyzed. The surface morphology and structure of the coatings were determined by scanning electron microscope ( SEM), X-ray diffraction analysis (XRD) and EDS, to study the effect of the content of boric acid in the plating bath on the Ni-Mo-P chemical deposition process conditions. The scale laboratory tests were used to measure the scaling performance of the Ni-Mo-P alloy coatings. Results The results indicated that the addition of the heteropolyacid salt containing molybdate ion had stabilizing effect on the Ni-Mo-P chemical deposition. Moreover, the optimal process conditions of Ni-Mo-P chemical deposition were 16. 5 g / L of NiSO4 ·6H2 O, 20 g / L of NaH2 PO2 ·H2 O, 0. 5 ~ 0. 8 g / L of sodium molybdate, 2 g / L of boric acid,and 7. 5 g / L of sodium acetate. The scaling rate of the electroless Ni-Mo-P alloy coating was obviously lower than that of the electroless Ni-P coating, showing good scaling protection properties, and amorphous coating was formed. Conclusion To obtained amorphous Ni-Mo-P alloy coating,by using the electroless plating deposition on the substrate Ni-P coating, boric acid have the capable of regulating pH and the complexing properties of the bath, amorphous Ni-Mo-P alloy coating minimum average rate of fouling is 0. 58 μm/ h, with the better scale capacity.