Abstract: Four biological agents, water retaining agent(TⅠ), ABT (TⅡ), CCC (TⅢ) and PP333(TⅣ), were applied to 2yearold desert plant Yucca brevifolia seedlings to study the effect and function of these biological agents on survival rate, growth, physiological and biochemical indexes of it, and a comprehensive evaluation on their impact efficiency was drawn out. The results were as follows: TⅠ and TⅡ significantly increased the survival rates of seedlings, which were 10.78% and 5.43% higher than CK; but survival rates of TⅢ and TⅣ were 15.78% and 11.25% lower than CK. TⅠ significantly promoted the growth of Y. brevifolia seedlings and increased photosynthetic physiology indexes, content of osmoregulation substances, the activity of POD and CAT of Y. brevifolia seedlings. Compared with CK, TⅡ made no significant changes on the growth index, but both antioxidant enzyme activity and proline content of TⅡ were significantly higher. TⅢ made the height of seedlings significantly lower than that of other treatments, and it mainly had effects on the free proline content and antioxidant enzyme activity indicators of the seedlings. TⅣ thickened the diameter and shortened the height of seedlings, and had an impact on photosynthetic and SOD activity. Through principal component analysis, plant type and photosynthetic physiological factor had the maximum weight in a comprehensive evaluation of Y. brevifolia seedlings, as 68.11%; Dvalue was in the sequence of TⅠTⅣTⅡCKTⅢ. It revealed that water retaining agent was the best biological agent, which had significantly increased the survival rates and physiological and biochemical indexes of Y. brevifolia seedlings, and notably promoted its growth at the same time. Next to it was ABT3, which had significantly increased the survival rate by influencing the indicators of osmotic adjustment substances and antioxidant enzyme activities. Although PP333 had a greater impact on the survival rate of plants, its concentration might be unsuitable to its survival. Its concentration for application needs to be further studied.