Lithium ferrite (LiFe5O8) nanocrystallites ranging from several nanometres to several hundreds of nanometres in size have been prepared by the polyethylene glycol gel method. These nanocrystallites were identified as pure lithium ferrite by x-ray diffraction analysis. Their magnetization and de-magnetization were measured by using a vibrating sample magnetometer at different temperatures. The specific saturation magnetization and the coercivities change with the diameter of these nanocrystallites and with temperature. The effective magnetic anisotropy constants KE of these samples were deduced by using the law of approach to saturation. It is found that the KE value of a lithium ferrite nanocrystallite of diameter 9.1 nm is about ten times greater than the magnetocrystalline anisotropy constant K1 of bulk lithium ferrite. The coercivities of these nanocrystallites at different temperatures were calculated by using the mixed coercivity model. The calculated coercivity results are consistent with the experimental ones.