The guest-host polymer system of nonlinear optical (NLO) polymers was investigated. The thermal stability of the polymer system was shown by the time dependence of the piezoelectricity of the poled polymer. The parameters measured in the experiment were the glass transition temperature, the orientational order parameter, and the electro-optical coefficient. The disadvantages of guest-host polymer systems were overcome by using a high glass transition temperature host polymer polyetherketone (PEK) doped with organic chromophore.