Abstract: Ultramarine is an important pigment with a bright color, which is used for the shield of PVC-U profiles, and however, its molecular structure makes ultramarine especially vulnerable by acid. The development of acid-resisting ultramarine is necessary for improving the comprehensive performance of PVC-U profiles. This paper reported the acid-resistant tests for an acid-resisting ultramarine pigment by the addition of HCl and also presented the comparison results of extrusion test for different types of ultramarine pigments. An investigation was conducted for the effects of different types of ultramarine on the processing properties and weatherability, coloring property and glossy degree, and the obtained results might provide a reference for the use of ultramarine pertinent in PVC-U profiles.