The activity of symbiotic -fixation and environmental factors of Robinia pseudo-acacia L., bearing root nodules, were quantitatively analyzed during the growing period. Among changes of total nitrogen and phosphorus contents of each organ, leaves showed prominent decreases from the highest quantity of the early growing period to the lowest of the late period. The rhizosphere showed acidic pH and low level of nitrogen, phosphorus and organic matter contents during the growing period. -fixation activity of nodules initiated from April and showed the maximum value of 190 $mu$/g DW/hr in late June and than decreased to 50$mu$M/g DW/hr during the rainy and dry season. Another peak of the activity attained 246$mu$M/g DW/hr in the late growing stage of September. The maximum value of nitrogen fixation activity was observed at the conditions of pH7, $25{circ}C$ of temperature and 20 Kpa of oxygen partial pressure.