Magnetite(Fe3O4) powders were synthesized through glycothermal reaction by using crystalline $alpha$-FeOOH as precursor and ethyleanne glycol as solvent. The phase, morphology and particle size of synthesized powders were characterized by XRD and an SEM. When only ethylene glycol was used as solvent, the phase was transformed from $alpha$-FeOOH to $alpha$-Fe2O3 and finally Fe3O4 at 27$0^{circ}C$ for 6hr without morphological change. But by addition of water, Fe3O4 powders were synthesized at 23$0^{circ}C$ for 3hr through solution-recrystalization process. As the content of water addition increased, the particle shape changed from sphere to octahedron and the partcle size increased. When the excess amount of water added, residual $alpha$-FeOOH or $alpha$-Fe2O3 was recrystalized.