This article detects the shape of objects based on the flexible fibre optic grating ( FBG) sensors encapsulated in PDMS material. The influence of the number and layout of sensors on the reconstruction accuracy of objects of different shapes is discussed. The accuracy of the algorithm is evaluated by using COMSOL simulation software. Four FBG flexible sensors are designed and calibrated for curvature. The sensors are distributed on the aluminium plate. The minimum relative errors for the equally distributed 3 and 4 FBG flexible sensor reconfiguration are -6. 12% and 0. 48% , respectively. Experimental results show that the reconstruction is better when 4 sensors are utilized. Therefore, by selecting 4 sensors in 7 different sets of dispositions, the layout has small relative error under the condition of 4 different weights. The specific is that the interval values of one end of the aluminium alloy plate are 260, 100 and 90 mm, respectively. For the other end, the interval values are 150, 150 and 150 mm, respectively. The effect of reconstruction is well and all have the smallest relative errors in the seventh group of 6. 22% , -1. 01% , -2. 52% , and -3. 22% , respectively. The designed FBG flexible sensor provides the basis for applications in the field of soft robot shape reconstruction.