The importance of the effective temperature factor in X-ray analysis was shown by presenting the results of measurement of the effective Debye parameter B_{e f f} on some crystalline samples.Calcium fluoride precipitated from Ca (OH) ₂ by HF had three times larger value of B_{e f f} than the commercial reagent grade one.This value corresponded to the value after grinding of reagent grade CaF₂ for more than 20 hrs.Rutile formed by the phase transformation from anatase with very fine grain was found to have relatively large value of B_{e f f} at the beginning of transformation.It was shown that very large error in the quantity of the crystalline phase might be introduced from the neglect of the effective temperature factor if intensity of the diffraction line at high angle side was used.It was also shown to obtain more reliable results on the ion distribution in spinels (GeCo₂O₄ and CoAl₂O₄) by finding the one gave the best linearity between log (I_obs/I_calc) and (sin ²θ/λ²).By this revised method, the effect of the difference in the effective temperature factor from specimen to specimen on the conclusion can be neglected.