The invention relates to the field of refractory materials, particularly to a microporous mullite light aggregate and a production method thereof, and solves the problems of the prior art, such as large volume density, poor compression strength and fire resistance, high heat conductivity, large pore size and non-uniform pore distribution. The light aggregate is made from bauxite, coal gangue, sawdust and petroleum coke. The production method comprises the following steps: crushing raw materials respectively, mixing thoroughly, adding water 80-85% the total weight of the raw materials, wet-milling, filtering with a screen mesh, molding under 6-8 MPa, drying at 180-200 DEG C for 65-75 h, calcining at 1400-1450 DEG C for 9-10 days, crushing, and sieving to obtain mullite light aggregate. Theproduct has the advantages of high porosity, less volume density, small average pore size, small heat conductivity, high compression strength and good fire resistance. The product is widely used as heat-insulating material or directly used in work lining and roof of various industrial furnaces such as heating furnace.