The effects of fly ash, sludge and straw on the density grade of muck ceramsite were studied. According to the optimization of raw material formula and process parameters, the muck ceramsite with a density grade of 700900 was fabricated, and their macroscopic performance and microstructure were analyzed. The results indicate that the apparent density of muck ceramsite gradually decreases with increasing content of fly ash, sludge and straw when the sintering temperature is 1 150℃, the muck fly ash is the most appropriate mixture. The 700900 density grade muck ceramsite with different sizes can be fabricated with muck of 60%83% and fly ash of 17%40% at the sintering temperature of 11701250℃. With the muck ceramsite density grade from 900 to 700, the cylinder compress strength was reduced from 126MPa to 49MPa. And the pore diameter in muck ceramsite of the smaller density grade is larger than that of the larger density grade, in addition, there are more connected holes under the same particle size.The ratio of the closed pore in the small particle size is higher, and the pore structure density is larger than that of the large particle size under the same density grade muck ceramsite.