Mullite whisker 3-D network with controllable size can be obtained via direct sintering from coal gangue and bauxite in lithium chinastone-MnO2-CaCO3 complex catalyst. The unique "bird's nest"-like structures consist of uniform mullite whiskers with a width of 200 nm and length of up to 3-5 mu m, which exhibit excellent flexural strength (165.61 MPa) with a relatively low density (1.55 g cm(-3)). The sizes and shapes of mullite crystals can be controlled by changing the content of lithium chinastone. The possible formation mechanism of "bird's nest"-like mullite whisker 3-D network structure was also discussed.