Lithium fluoride (LiF) thermoluminescent powder doped with Mg, Cu, Na, and Si as activators was prepared. X-ray diffraction analysis indicated that doping LiF with different activators makes crystal lattice somewhat expand. The dosimetric properties of the powder were studied. The main dosimetric peak of LiF:Mg,Cu,Na,Si appeared in the range of 227−247o C and the ratio of the height of the main peak to that of the other small peaks in the LiF:Mg,Cu,Na,Si is much greater than that in the LiF:Mg,Ti and LiF:Mg,Cu,P. .