Perovskite TbMO3 (M=Fe, Mn) have shown many interesting magnetic properties, e.g., multiferroics in TbMnO3, spin soliton lattice in TbFeO3. Their solid solution TbMn1-xFexO3 also exhibits intrigue magnetic properties and structure.After entensive investigation through magnetometry and other measurements, an rich magnetic phase diagram has been established. However, our preliminary study shows that some points are really questionable. Here we propose neutron powder diffraction experiment aiming to clarify this obscure. A serial solid solution samples TbMn1-xFexO3 will be measured the diffraction pattern at various temperature. Magnetic symmetry and structure analysis will be preformed to establish a correct phase diagram and understand the recently observed novel property.