Two X-type chromophores, 2-[4-(4,5-di(4-nitrophenyl) imidazolyl) phenyl]-4,5-di(4-methoxyphenyl)-imidazole (DNPIPDMOPI), 2-[4-(4,5-di(4-nitrophenyl)-imidazolyl) phenyl]-4,5-di(4-aminophenyl)-imidazole (DNPIPDAPI), were synthesized and characterized. The results show that they possess good nonlinearity, considerable blue-shifted absorption (385 nm and 379 nm in THF) and high decomposition temperature (377 “C and 405 ”C). These mean that the X-type chromophores possess a rather good nonlinearity-transparency-thermal stability trade-off. The multi-step corona-poling technique at elevated temperature and in-situ SHG measurements were used to obtain and evaluate the poled films of these chromophores doped in PMMA. The largest SHG signals appeared at 110-120°C, which are 12.5 pm/V and 16.7 pm/V respectively. The dependence of poling induced orientation stability on temperature was measured by depoling experiments and the results indicate that the poling-induced orientation of the films is stable at about 100°C. Theoretic analyses imply that better orientation stability arises from the X-type structure of chromophore. The X-type chromophore has two crossed intramolecular CT, both β xxx and β xyy can contribute to the second-order susceptibility, and the ratio of the tensorial components (γ= β xyy /β xxx ) is about 1/3, so the orientation decay of the films induced by rising temperature will provide a certain compensation for the contribution of β xyy of chromophores. Two X-type chromophores, 2- [4- (4,5-di (4-nitrophenyl) imidazolyl) phenyl] -4,5-di (4- methoxyphenyl) -imidazole (DNPIPDMOPI) , 5-di (4-nitrophenyl) -imidazolyl) phenyl] -4,5-di (4-aminophenyl) -imidazole (DNPIPDAPI), were synthesized and characterized. The results show that they possess good nonlinearity, (385 nm and 379 nm in THF) and high decomposition temperature (377 “C and 405” C). These mean that the X-type chromophores have a good good nonlinearity-transparency- thermal stability trade-off. The multi- step corona-poling technique at elevated temperature and in-situ SHG measurements were used to obtain and evaluate the poled films of these chromophores doped in PMMA. The largest SHG signals appeared at 110-120 ° C, which are 12.5 pm / V and 16.7 pm / V respectively. The dependence of poling induced orientation stability on temperature was measured by depoling experiments and the results that that poling-induced orientation of the films is stable at about 100 ° C. Theoretic analyzes imply that better orientation stability arises from the X-type structure of chromophore. The X-type chromophore has two crossed intramolecular CT, both β xxx and β xyy can contribute to the second-order susceptibility, and the ratio of the tensorial components (γ = β xyy / β xxx) is about 1/3, so the orientation decay of the films induced by rising temperature will provide certain certainty for the contribution of β xyy of chromophores.