A novel nonlinear organic ionic material, or pyrylium salt dye, is synthesized and doped in the polymer matrix. These guest‐host‐type polymer films, which have no absorption in the blue‐wavelength region, have second harmonic generation (SHG) activities without the electric‐field poling process. The nonlinear optical coefficientd33is estimated as 1.10 pm/V at a 15 wt % of dye concentration. The nonlinearity is stable at room temperature and at 120 °C. The SHG device is fabricated using the nonpoled polymer film, and Cerenkov‐type phase‐matched SHG is observed. ©1996 American Institute of Physics.