Firstly, several kinds of bentonite modification methods and its application in papermaking were investigated. The retention and drainage effects of the CPAM/bentonite system were characterized by fines retention and freeness. It was found that Bentonite modified with the mixture of Na2CO3 and an organic salt greatly improved the retention and drainage effects, therefore, it was a good modification method. The modification condition and mechanism were discussed further. The retention and drainage effects were compared between the Bentonite modified with the mixture of Na2CO3 and the organic salt and imported bentonite, and it was found that modified bentonite reached the level as imported bentonite. Secondly, it was studied that the retention and drainage effects of added amounts of CPAM, bentonite, aluminium sulfate and electrolyte concentration (NaCl) on CPAM/bentonite microparticle retention and drainage aid system, etc. On CPAM/bentonite system, it was found that the retention and drainage effects of a higher electronic density CPAM was better than lower electronic charge density CPAM, which was different from Agne Swerin' s view of point. An increase in the electrolyte concentration (NaCl) resulted in less retention and drainage effects. However, the retention and drainage effects in CPAM/bentonite system was maintained up to a higher NaCl concentration than single CPAM system. It was meaningful to white water recycle system. The mechanism of retention and drainage effects of CPAM/bentonite microparticle retention and drainage aid system was analyzed with electrochemistry method. It was shown that the key point was to keep fibers negative to get good retention and drainage effects. Therefore, CPAM/bentonite system was not fit for acidic paper making method. In the other hand, it was investigated that the application of CPAM/bentonite system on treating the paper making mill's effluent. It was found that CPAM/bentonite system had splendid effects on effluent treatment, and the cost was lower than traditional aluminium sulfate /CPAM method, and the pollution of Al3+could be avoided. Finally, flocculation Mechanism of microparticulate retention aid system was investigated. Britt dynamic drainage jar (DDJ) was used to judge the flocculation mechanism. The results showed that microparticulate retention aid system had more efficient retention than CPAM retention aid system. Bentonite increased the bond strength of polymer layers adsorbed on fibers and GCC due to high specific surface area and charge density of bentonite. This study investigated the retention of GCC on fibers using CPAM and bentonite as retention aids, the same mechanism should be fit for the retention of other anionic colloids, such as fines and pitch, etc.