The purplish soils with the different properties and fertility had obvious influence on nodulation and nitrogen fixation of the alder. More nodule numbers and higher N₂-fixing capacity occurred on two Shaqimiao purplish soils and Penlaizhing calcium light loam, but less nodule numbers and lower Ns-fixing capacity was found on the heavy loam with high calcium content. and the strongly acid soils. The soil temperature in the range From 20°-32℃ was more suitable to N₂-fixing activity. It was obvious that the activity declined gradually with decreasing of temperature below 20℃. Deficiency or excess of water in the soil could cause the tremendous decline of the nitrogenase activity. Planting the alder on various purplish soils may increase soil nitrogen and be beneficial to soil amelioration.