In order to explore the changes of second-harmonic generation in poled polymer at different temperatures and different densities，the PMMA doped azo-dye films were studied by real-time corona polarization device.The experimental results show that for this host-guest system,second harmonic generation intensity showed a trend of first increase and then decrease;At optimum polarization temperature,SHG intensity increase first then decrease as the density of azo-dye molecules raise.Analyzed on the basis of absorption spectra,we propose a new interpretation that as the density raise the value of first-order hyperpolarizability of azo-dye molecules changed,so SHG intensity changed.