The invention is a chemical surface decoration process for silicon micro type electret voice sensor electricity storing film. It uses glass container with air extracting valve, its bottom is arrangedwith solution HMDS or DCDMS, the top is arranged with pile film Si plate containing SiO2 or Si3N4/SiO2, under the pure saturate steam of the solution, carries on air phase reaction, avoids the film from being contaminated by water or other active substance, the invention can improve electret state of SiO2, Si3O4/SiO2, guarantees the stability of charge storage.