A glaze with a good quality and a unique decorative pattern was prepared with purple clay as a source of iron, Ca3(PO4)2 and SnO2. The effect of addition agents on the glaze color, microstructure and artistic textures was investigated by ultraviolet-visible spectroscopy, X-ray diffraction and scanning electron microscopy, and the color mechanism was analyzed. The results illustrate that the introduction of addition agents changes the chemical state of iron, and contributes to the formation of blue fancy glaze. The introduction of Ca3(PO4)2 can cause the partial reduction of iron ions, leading to the glaze appearing blue and yellow, and Ca2+ ions promoting the separation of liquid phase to produce blue patterns. Also, the introduction of Ca3(PO4)2 and SnO2 for the increased reducibility of iron ions can increase the ratio of Fe2+ and Fe3+ ions, resulting in the glaze being blue-green, and the greater pattern and lightness value L*. The presence of Fe3+―O―Fe2+ in the vitreous is one of the color factors. The liquid separation forming the structure of the color is the auxiliary color of glaze color. The combined chemical color with structural color on the glaze becomes more colorful.