Based　on　fractional　Brownian　motions　and　discrete　Fourier　transform,　the　traditional　characteristic　parameters　of　fractal　profiles　were　studied.　It　is　found　that　with　given　sampling　points,　if　the　double　logarithmic　power　spectrum　of　a　fractal　profile　is　assumed　to　be　linear,　the　quantitative　relationship　between　the　profile＇s　root　mean　square　roughness　and　its　fractal　parameters　can　be　established　based　on　the　theorem　of　Parseval.　And　because　of　the　randomness　of　phase　spectrum,　the　material　ration　and　arithmetic　average　height　of　the　profiles　are　still　different　even　though　the　fractal　parameters　are　the　same.　Through　enough　random　experiments,　a　profile　with　given　fractal　parameters,　root　mean　square　roughness,　bearing　rate　and　arithmetic　average　height　can　be　synthesized.