An air purifier includes a shell, a wind turbine and an air filter layer. The shell includes at least one air inlet and at least one air outlet, and an air passage is defined between the at least one air inlet and the at least one air outlet. The wind turbine is located in the air passage. The air filter layer is located in the air passage and includes a filter screen. The air filter screen includes a carbon nanotube structure including a plurality of carbon nanotube films stacked and crossed with each other. The carbon nanotube structure includes a plurality of micropores. A diameter of the micropores is ranged from about 1 micrometer to about 2.5 micrometers.
