The impact of highly cationic density polymers such as modified poly-ethyleneimine(PEI), as anionic trash catcher(ATC) on the drainage and retention properties of aspen alkaline hydrogen peroxide mechanical pulp(APMP) in different CPAM(/bentonite) systems was studied. The results showed that Modified PEI could improve the retention and drainage properties of CPAM/ bentonite systems; when adding 0.02% dosage of PEI, the drainage and retention rate were increased by 16.0% and 1.9% respectively as compared to control with 0.03% dosage of the CPAM with 1.55 meq/g cationic charge density and 4.9 million molecular weight, which denoted by CPAM(W/W); the drainage and retention rate were increased by 28.6% and 3.0% respectively as compared to the control with 0.03% dosage of CPAM(W/W) and 0.3% dosage of bentonite. The CPAM with more cationic charge density and higher molecular weight than the CPAM(W/W) is denoted by CPAM(W/O) in this paper. The microparticle system which consisted with PEI and the CPAM(W/O)(/bentonite) was slightly superior to the PEI/CPAM(W/W)/bentonite system. When 0.02% dosage of PEI and 0.03% dosage of CPAM were added respectively, PEI/CPAM(W/O) made the drainage and retention rate increased by 9.5% and 1.9% respectively as compared with PEI/CPAM(W/W).