The critical conditions of solidification orientation for Solidification of giant magnetostrictive materials R-Fe alloy in a magnetic field have been investigated. The experiment results show that suppressing the turbulence in melt is a key factor in texturing the magnetic materials. In solidification course, the turbulent degree in melt is dominated by the cooling rate, and a modified Ra^m number is used to simulate the state of turbulence at various cooling rates. While the value of the critical Ra^c number in magnetic field is large than that of the modified Ra^m number in melt, the temperature oscillations in melt will be restrained, and the texture along the easy magnetic axis will be dominant in the sample. Therefore the critical conditions of effective orienting action for magnetic materials by solidification in a magnetic field can be definite as the rate of the critical Ra^c number in a magnetic field to Ra^m number in melt is close to 1.