The invention provides photocatalytic powder capable of being applied to environment purifying and atmospheric pollutant governing. Each titanium dioxide particle is wrapped by a hydroxyl apatite layer, and holes with controllable size are formed in the hydroxyl apatite layer, so that target products such as formaldehyde and benzene are selectively degraded, and other larger molecules such as methyl orange are not damaged. The photocatalytic chemical powder can be extensively applied to various organic polymer setting products, especially organic fibers, plastic products or paint.