Optical fiber Bragg grating (FBG) has been widely used to detect strain. Nevertheless, uneven strain is easy to cause deformation of FBG spectrum, which will result in the invalidation of wavelength detection. Therefore, it is necessary to reconstruct the strain along FBG. In response to that traditional strain distribution reconstruction theory both have poor effect and slow convergence speed, strain distribution reconstruction theory based on FBG central wavelength and reflectivity of spectrum dual constraint is presented after deep research on improved genetic algorithm, which significantly improves the non uniqueness and the confidence of reconstruction. At the same time, assuming distribution of strain is polynomial, reconstruction of strain distribution is realized through reconstructing the coefficients of the polynomial, which has improved the speed of strain distribution reconstruction. And then strain parameters reconstruction numerical simulation experiments are comprehensively carried out, and the errors of the reconstructing polynomial coefficients are all less than 1.5%. Through tuning FBG by two ends fixed compression bar experiment, the validity, applicability and practicability of the novel reconstructing method have been verified. Consequently, a novel method of reconstructing strain distribution which is fast and efficient has been generated.