A strain detection and reconstruction system was developed to monitor deformations on spacecraft plate surfaces. To this end， a displacement field reconstruction method was proposed based on fiber Bragg grating sensors and an incremental extreme learning machine （I_ELM）. A four sided fixed support flat plate device was designed for strain detection and deformation reconstruction. Each of its panels had 12 sensors evenly distributed in a 4×3 grid. The accuracy and stability were improved by completely sticking method. A model for predicting structural deformation was then designed based on I_ELM. The model could effectively predict structure deformation displacement after training. Finally， 3D restoration was realized after incorporating cubic spline interpolation. The average absolute error of the proposed approach was less than 0.05 mm and root mean square error was less than 0.005 mm. Therefore， this method can be used to monitor the deformation of spacecraft surfaces.