Fluidized bed reactor vapor deposition(FBR VD) was utilized to modify fly ash, in which NaOH or Na2SO4 was deposited onto the surface of the fly ash beads. The crystallization and leaching processes were investigated by scanning electron microscopy(SEM) and Fourier transform infrared spectrometer(FTIR). The strength developments of cement paste and mortar with modified fly ash were analyzed. The hydration process of cement paste was investigated based on SEM and X ray diffractometer(XRD). Results figure out that leaching happens between fly ash and NaOH, breaking the Si—O bond and improving the hydration activity of fly ash. The crystals of Na2SO4 are smaller in size and better distributed and it remains undissolved in the cement paste, which enhances the hydration of the fly ash as well as the cement clinker nearby. These two effects may strengthen the anchor between the cement matrix and the fly ash and benefit the strength development. When the contents (by mass) of NaOH and Na2SO4 are 0.23% and 1.17% respectively, higher strengths of the cement paste and cement mortar are achieved, as compared to those with traditional chemical activation.