Preparation method of porous mullite ceramic applicable to diesel particulate filter

The invention relates to a ceramic preparation method, particularly to a preparation method of porous mullite ceramic applicable to a diesel particulate filter. The preparation method comprises the following steps: mixing kaolin, bauxite, a crystallization catalyst AlF3 and a sintering aid, specifically, firstly, uniformly mixing kaolin and bauxite, and then adding the crystallization catalyst and the sintering aid; adding deionized water and a dispersing agent; pouring the mixture into a polyethylene mold; placing the mold in a refrigeration device for directional solidification, so as to form a ceramic body; placing the ceramic body in a freeze dryer for drying; carrying out pressureless sintering on the dried ceramic body in an alumina crucible, so as to obtain the porous mullite ceramic. According to the preparation method, the traditional technology is broken through, and the porous mullite ceramic prepared through the freeze-drying technology is relatively high in porosity and has directionally communicated straight channels, so that the pressure loss during the filter process can be reduced.