The microstructure of cationic gemini surfactant 1,6-bis(dodecyldimethylammonium) hexane dibromide C12H25(CH3)2N-(CH2)6-N(CH3)2C12H25·2Br] (12-6-12·2Br-) and oppositely charged polyelectrolyte poly(acrylic acid,sodium salt) (NaPA) in aqueous solution has been studied by using fluorescence, conductivity measurement, freeze-etching and TEM. The data obtained from fluorescence and conductivity measurement show that micelle-like or complex can form between the gemini surfactant (12-6-12.2Br-) and polyelectrolyte NaPA due to the static electric interaction and hydrophobic forces. Through freeze-etching and TEM, the microstructure of the mixture solution has been studied, which is consistent with the result from micropolarity. Comparing the fluorescence spectrum of system of dodecyltrimethylammonium bromide (DTAB) and NaPA with that of system of gemini surfactant (12-6-12.2Br-) and NaPA, it can be found that the interaction of (12-6-12.2Br-) and NaPA in aqueous solution has also been detected. It can be shown that the precipitate will transform into gel in higher NaPA concentration.