A guest-host system of a nonlinear optical (NLO) arylphosphine oxide and polyhydroxystyrene (PSOH) has been investigated for second-order nonlinear optics. The synthesized NLO-active arylphosphine oxides show spectroscopic properties in accordance with the proposed structures using n.m.r. spectrometry. These NLO-active arylphosphine oxides and polymer matrix exhibit optical transparency down to 400 nm, and excellent thermal stability (T-d > 345 degrees C). An NLO-active chromophore with short absorption wavelength is desirable for application in frequency doubling. Moreover, the excellent thermal stability of the chromophore will prevent its decomposition during the poling process at elevated temperatures. The homogeneity of these guest-host NLO polymers are confirmed using scanning electron microscopy (SEM). The second-order nonlinearity and temporal stability of these NLO polymers were also reported. The relationship between molecular motion and temporal stability are studied by dielectric analysis.