Abstract: Nowadays, a new "AB" dual-colour coated moissanite has appeared in the jewelry market, exhibiting an unique blue-purple dual-colour visual effect on its crown, which shifts with viewing angles. In this study, the coating compositions, structural characteristics, and colouration mechanism of the "AB" dual-colour coated moissanite sample was analyzed using the microscopic observation, Raman spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), ultraviolet-visible spectroscopy (UV-Vis) and X-ray photoelectron spectroscopy (XPS) deep etching. The results indicate: (1) Microscopic observation revealed that the crown region of moissanite is covered with a coloured coating; (2)UV-visible spectroscopy revealed distinct reflection bands in the blue and violet regions; (3) Raman spectroscopy detects the characteristic peaks of moissanite, located at 775, 795, 963, 1 513, 1 692 cm^-1, corresponding to 4H-SiC type; (4) SEM-EDS revealed that the main constituent elements are Zr, Si, C, and O in the crown region of the sample; (5) XPS deep etching further confirmed that the surface coating elements are Zr, Si and O. It is thus inferred that the coating composition is ZrSi_xO_y, with the coating thickness exceeding 100 nm. The simulation analysis of the film structure revealed that the colouring mechanism of the "AB" dual-colour coated moissanite is attributed to structural colour generated by the interference of the coated single-layer film.