Taking the advantage of fiber Bragg grating (FBG) applied in vibration detection into account, a kind of FBG medium-low frequency acceleration sensor base d on symmetrical gemel is designed.In this paper,the structure and the operation principle of the se nsor are proposed,and a fitting method to calculate the stiffness of gemel is brought up.At the same time,the theoretical formulas of nature frequency and sensitivity of the FBG acceleration sensor are deduced.By optimizing the structure parameter of the sensor in SQP from two different routes,two structure size results that can meet different practical needs are received.At last, in order to verify the accuracy of the theoretical formula,the sensor is tested from three aspects of t he sensitivity,the amplitude-frequency response feature and the transverse anti-interference abil ity through calibration experiment on the vibration table.The experimental results show that the senso r resonant frequency is about 400Hz,and the sensitivity is approximately 230pm/g,which are both fundam entally consistent with the theoretical calculation.What is more,the transverse response amplitude is less than 8%.It shows that the FBG acceleration sensor designed in the paper is equipped with a good t ransverse anti-interference ability.