Abstract: Below-ground competition is one of the major factors that induces structural changes of plant community in agriculture or nature ecosystems.Elevated CO₂ can directly or indirectly influence plant growth and below-ground environment,and consequently plant competition for underground nutrients.This paper summarizes the effects of CO₂ enrichment on plant competition underground from the aspects of root structural morphology, root physiologically absorbing ability, mutual mycorrhizal, and soil environment by discussing the characteristics of plant underground competition under enriched CO₂ condition.