Abstract: Through adsorption-desorption experiment and incubation test,this paper studied the phosphate adsorption and desorption characteristics of several fly ashes.The test fly ashes contained 0.545～4.540 g·kg^-1 of total P and 19.55～163.0 mg·kg^-1 of available P,which were significantly higher than those in soils.The P adsorption capacity of fly ashes increased with increasing added P,while their P adsorption rate was in adverse.Fly ashes had a higher P adsorption rate but a lower P desorption rate than soils,mainly because fly ashes had more P adsorption sites and stronger bound energy.In this study,Langmuir,Freundlich,and Temkin equations were fit to the measured data,and the MBC value in Langmuir equation,a value in Freundlich equation,and k_{2> value in Temkin equation could be used as a comprehensive index to characterize the potential phosphate adsorptivity of fly ashes.The larger these values were,the stronger the P adsorptivity was.The MBC,a and k2> value of 5 fly ashes collected from different locations was in order of Xiangtan power factory （5 167.7,4 056.2 and 831.5） >Yueyang paper factory （1 650.7,2 803.4 and 711.9）>Huaneng power factory （303.0,1 677.6 and 368.7）>Zhuzhou power factory （34.7,413.48 and 213.8）>Dongting nitrogen fertilizer factory （34.7,413.48 and 213.8）.The P fixation by fly ashes generally increased with their increasing water content,and their phosphate adsorption was mainly specific adsorption and chemical precipitation,suggesting that the P fixation and the water content of fly ashes should be considered when fly ash was used as soil amendment or as compound fertilizer filling substance.}