The conversion from deflection tomography projection to phase tomography projection is analyzed, and an explicit expression corresponding to the conversion is presented. An error analysis is made to the reconstructed fields by filtered back-projection (DFBP) algorithm of deflection tomography. Results show that the effect of projection noise on the reconstructed fields is represented by a slope function related to the filter used in deflection tomographic filtered back-projection algorithm. So the deflection tomographic filtered back-projection algorithm is modified. Numerical simulation shows that the modified algorithm depresses the slope phenomena efficiently, while no obvious distortion is introduced to the reconstruction. Based on the modified algorithm, the three-dimensional reconstruction for density field of the real rocket exhausted plumes is carried out.