The invention relates to a surface modification and whitening method of a fly ash hollow microsphere belonging to the field of mineral material processing and environment control which comprises the following steps: stirring and dispersing the fly ash hollow microsphere and water, adjusting the pH value of the mixture and conducting precipitation reaction after adding aluminium sulphate and waterglass solution, coating alumina silicate on the surface of the fly ash hollow microsphere, reacting the mixed solution after adding aluminium sulphate and water glass solution for a certain time, filtering, washing, drying and depolymerizing the reaction product to get whitened fly ash hollow microsphere.