The influence of composition and temperature on the formation of solid solution x FeTiO3 (1-x) Fe2O3 were examined, using artificial materials. The mixture of pure ilmenite and hematite, sealed in a quartz tube under evacuated approximately below 10-3mmHg, was sintered in a furnace. The results obtained were as follows.1) Ilmenite and hematite begin to dissolve each other at the temperature above 600°C. At the temperature range of 600-700°C, solid solutions, having two compositions, were formed overthe wide range of the initial compositions. These solid solutions did not turn into a single composition even after sixty hours of sintering. Solid solutions, having the single composition, were formed above 800°C.2) At the temperature range of 600-800°C, spinel and rutile were formed with xFeTiO3 (1-x) Fe2O3 solid solutions. This phenomenon was most obvious at 700°C and about x=0.3. This spinel was identified as magnetite.3) There were two mechanisms to form x FeTiO3 (1-x) Fe2O3 solid solution. One is the formation of xFerTiO3 (1-x) Fe2O3 solid solution from the mixture of ilmenite and hematite. The other is the formation of magnetite and rutile from the mixture of ilmenite and hematite, followed by the formation of x FeTiO3 (1-x) Fe2O3 solid solution. The former was remarkable at the compositionof x≥0.6 and the latter was remarkable at the composition of about x=0.3.4) Solid solution x FeTiO3 (1-x) Fe2O3, excluding magnetite and rutile, are formed over the whole range of compositions at the temperature above 1000°C. The magnetization increased with the decrease ofx, reaching the maximum at x=6.65 and then decreased. The magnetization of solid solution with the composition x<0.5 was very small, while the solid solution with the composition x≥0.5 showed ferrimagnetism. The magnetization curves of the latters was saturated but that of solid solutions (x≥0.5) preparedby slow cooling method was not saturated even at 9400 Oe.5) When solid solution xFeTiO3 (1-x) Fe2O3 formed at 1200°C was maintained at lowertemperature for appropriate time, the magnetization increased. Therefore the magnetization of solid solution obtained by the slow cooling method is higher than thatof solid solution obtained by the quenching method.