The invention relates to a cement foamed heat preservation board. The cement foamed heat preservation board is processed from fly ash, common Portland cement and admixtures, and is prepared from, by weight, 10%-20% of the fly ash, 70%-85% of the common Portland cement, 1%-3% of a waterproof agent, 1%-3% of accelerator, 3%-5% of hydrogen peroxide and 1%-3% of polyvinyl chloride fiber. The sum of all components is 100%. A preparing method of the cement foamed heat preservation board comprises the steps that firstly, the fly ash and the common Portland cement are weighed and mixed according to needed doses; an appropriate amount of water is taken, the admixtures of the corresponding proportion are added to be stirred into a mixed solution, and the temperature is controlled at 50 DEG C-60 DEG C; the mixed material and the mixed solution are put into a stirrer according to the proportion of 1 to 0.5 to be mixed and stirred for 5-6 min, and then hydrogen peroxide is added to be mixed evenly to obtain foamed cement slurry; then foaming, demolding, and forming maintaining are conducted to obtain the cement foamed heat preservation board. The cement foamed heat preservation board has the advantages that the early strength is high, and the later strength is continuously improved.