The micro-powder of LaKFe2-xMOxO6 (x=0.45, 0.55, 0.65) was prepared by the sol-gel technique. After annealing, the the XRD spectrum of the samples which annealed at different temperature was tested and the influence on structure of the samples was studied. The samples belong to monoclinic system and the space group is P21/n by crystallographic plane index of diffraction peak of the main phase. The diffraction peaks of LaKFe2-xMOxO6 move to the right with the increased Mo doped in. The lattice parameters and volume decrease as x rise. The results show that the optimal doping ratio is obtained as x is 0.45 and the optimal samples of the series is LaKFe2-xMOxO6.The diffraction peaks ofLaKFe2-xMOxO6move to the right with the rise of temperature and the optimal annealing temperature of it is 1473K