In order to make better use of low - grade Ca - based bentonite for pellets production, semi - dry method is used to modify this kind of bentonite and the pelletizing test is carried out. The results show that, after the bentonite is sodium - modified by the best semi - dry method, the water absorption and swelling volume in 2 hours are increased from 161.1% and 3.1 mL/g to 349.03% and 18.1 mL/g, respectively. After the sodium modification and compound modification, when the proportion is 1.6%, the green ball falling strength increases from 3.9 times/(0.5 m) of the original soil to 5.4 times/(0.5 m) for sodium - modified soil and composite bentonite of 6.6 times/(0.5 m) respectively. In addition, after the modification of the composite soil, the proportion of the original soil in the pellets can be reduced from 1.6% to less than 1.0%, and the burst temperature of the composite soil pellets is higher than that of the original soil by more than 100 ℃.