How to control the exacerbation saline-alkali soil and recover to forest vegetation has been recognized as an important project of national science and technology supporting program of China, which is also a key issue of the soda alkali land rehabilitation. By using krilium of HPMA and PAA, as well as wood tar and vinegar as alkali-depressing and alkali-preventing agents, soil improvement experiments at heavy soda saline-alkali soil were carried out, and growth of planted poplar seedlings and the dynamic of soil pH and salt content were also monitored. We found following conclusions. Firstly, both addition of HMPA and PAA could improve the saline-alkali soil, and HPMA was better than PAA. HPMA addition together with the alkali-preventing agent(wood vinegar+wood tar+PAA spraying at soda alkali soil, then forming a compact layer to prevent salt and alkali movement from deep layer to surface layer) made soil pH and soil salt content sharply decreased 0.93 and 0.78%, respectively, and the height and diameter growth rates of poplar sapling were 241 times and 2.36 times higher than those at control. Comparing to the effect of HPMA, PAA addition made a 0.23 decrease in pH and 0.63% in soil salt content, and height and diameter growth rate of planted poplar were 1.43 and 1.07 times higher than those at control; Secondly, addition of film-topsoil agent could decrease the pH of surface soil to 8.87, but no changes found in other deep layers. The film-topsoil agent addition could change the exchange of salt between surface layer and deep layer of soil; thirdly, data of rhizosphere soil and non-rhizosphere soil indicates that the growth of poplar saplings could decrease soil salinity and pH value, and strengthen the effect of krilium (HPMA and PAA) addition.