A low-temperature fast-fired lightweight ceramic heat insulation plate and a preparation method thereof. The preparation method comprises: performing ball milling and powder spraying on a raw material containing foamable ceramic waste slag to prepare foamable powder, the foamable ceramic waste slag accounting for 80-100 wt % of the weight of the raw material; uniformly mixing 100 weight portions of the foamable powder with 3-15 weight portions of granular powder of a low-melting-point organic matter to obtain mixed powder materials; pressing the mixed powder materials under 10-20 MPa to prepare a ceramic green body; and firing the ceramic green body at a temperature of 1100-1170° C. to prepare the lightweight energy-saving ceramic heat insulation plate.