According to the demand of stress and strain field monitoring on the key area of main bearing structure of helicopter, it is necessary to study the corresponding distributed on-line monitoring technology and its strain field inversion method, so as to provide the assessment reference for structure health state and the real-time identification of the structure deformation of helicopter rotor blades. The finite element simulations of the single ended fixed supported aluminum alloy beam and plate structure are carried out by Patran/Nastran simulation software. The basic configuration rules of fiber Bragg grating sensor and resistance strain sensor are presented, and an inverse method is given for the strain field of a single ended fixed supported aluminum alloy structure based on the three-B-spline interpolation algorithm. On this basis, a distributed strain on-line monitoring system based on fiber Bragg grating sensor and resistance strain sensor is constructed. Research results show that the method is reliable and applicable.