【Objective】 Saline-sodic soils are widely distributed in the western part of the Songnen Plain. A variety of materials or measures have been used to improve soils in the process of long-term saline-sodic land management, and get great improvement effect. However, the improvement effect of these amendments on saline-sodic soils is mostly an assessment of individual factors, thus, the quantitative assessments for the impacts on multiple soil functions of different amendments are still lacking. 【Method】 Based on this, Our study used a meta-analysis to obtain 854 sets of relevant data from 589 papers on the improvement of saline-sodic soils in the past 30 years. The improvement effects of gypsum type amendment, biochar, and mixed amendments (combined application of 2 or more amendments)on saline-sodic soil and the factors influencing the improvement effect were quantitatively evaluated and analyzed with a meta-analysis and the Random Forest method. 【Result】 The results showed that the effects in saline sodic paddy fields of the three amendments on decreasing alkalinity were –29.1%, –38.6%, and –41.1%, respectively, and the effect of improvement was significant, however, the difference in improvement effectiveness between amendments was not significant. Furthermore, biochar (47.7%) had the best effects on improving soil nutrient content, while gypsum-type amendments (26.3%) were relatively the lowest. The three amendments were mostly used for soil amendment at the top soil layer (0～20 cm) of moderate and heavy saline-sodic soils, and there were differences in the application amount and application duration on the effect of soil improvement. Amendment application amount was a significant factor affecting the effectiveness in reducing soil salt/alkali of gypsum type amendments. 【Conclusion】 The main working principle of gypsum-type amendments is to reduce soil alkali, indirectly enhance soil nutrients and promote crop growth, whereas biochar and mixed amendments have the combined effect of reducing soil alkali and directly promoting soil nutrients. The selection of soil amendments should take into account not only the amount, but also the crop types, the cost of the amendments, the durability of the effect, and environmental safety issues.