The invention discloses a high-intensity baking-free brick and a preparation method thereof. The preparation method comprises the following steps of mixing and stirring portland cement with coal cinders, fly ash, stone powder, sand, volcanic cinders, lime, silicon dioxide, calcium oxide, water and an additive so as to obtain a mixture M; performing compression moulding on the mixture M so as to obtain baking-free brick blanks N; and stacking the baking-free brick blanks N, and performing maintenance so as to obtain the high-intensity baking-free brick. The problems that the intensity of a conventional baking-free brick is not enough and a cracking phenomenon is easy to appear under high temperature environment are solved.