Abstract: The heat-stability of four kinds polyelectrolytes, HPAM, Spu(1), Na-CMC, and; FGLSwith different structures from each other, has been studied by the following methods: viscometry, conductimetric titration, IR, TGAand oxyluminescence.The changes of molecular weight and molecular structure, the results of TGAand the activation energies of oxidation as well showed that the heat-stabilities were in the following order:Spu(1)>FCLS>HPAM>Na-CMC.The heat-resistence of the drilling muds treated by these polyelectrolytes related closely to their structures.