This　paper　presents　the　theoretical　analysis　of　capillary　absorption　dynamics　for　cemementitious　material.　Fractal　theory　is　applied　to　analyse　tortuosity　of　capillary　pores　in　cementitious　material　and　a　definition　of　tortuosity　is　given.　The　dynamic　equation　of　capillary　absorption　considering　water　evaporation　and　tortuosity　of　capillary　pores　is　derived.　Based　on　the　dynamic　model,　the　capillary　coefficient　and　sorptivity　of　concrete　are　explained　theoretically.　In　absorption　test,　water　evaporation　is　one　of　the　main　reasons　caused　variations　from　linearity　between　water　absorption　height　and　the　square　root　of　time,　or　between　water　amount　absorbed　and　the　square　root　of　time.　In　cementitious　material,　the　evaporation　rate　is　very　small　compare　to　capillary　flow　velocity　at　the　initial　time　of　absorption　test.　For　simplification　of　testing　procedure,　there　is　no　meaning　to　modify　absorption　test.