The invention provides a fiber grating micro vibration sensor. The fiber grating micro vibration sensor comprises a support, wherein the support is a U-shaped structure and comprises a first side wall and a second side wall; the inner side of the first side wall is provided with a first step; the top end of the second side wall is provided with a beam which extends toward the first side wall; the outer side of the second side wall is provided with a second step and a third step; an adjusting beam is arranged on the second step; a compensation pillar is arranged on the third step; a vertical slot is formed in the second side wall; an inverted-T-shaped elastic sheet is arranged on the support; the head of the elastic sheet is fixed on the first step at the inner side of the first side wall; the tail of the elastic sheet is fixedly connected with an upper mass block and a lower mass block; an upward folding sheet is arranged at the middle part of the elastic sheet; a first micro hole is formed in the folding sheet; the adjusting beam comprises a vertical plate and a horizontal plate; a flange is arranged at the bottom of the vertical plate; a guide slot is formed in the second step; the flange is coordinated with the guide slot to enable the flange of the adjusting beam to be pivoted in the guide slot; and the vertical plate of the adjusting beam is connected with the second side wall of the support through a first fastening screw.