In traditional sub-carrier allocation process

user with the highest priority can choose best sub-carrier

which will result in low utilization of sub-carriers.Current improved algorithms can im-prove system capacity and reduce algorithm complexity by sacrificing certain fairness

but they may not achieve fairness requirement among users.In order to solve this problem

a new adaptive resource allo-cation algorithm based on fairness threshold was proposed

in which the priority of the sub-carrier allo-cation was determined by fairness threshold to achieve a rough tradeoff between capacity and fairness.Then power allocation base on particle swarm optimization（PSO） was introduced to realize the required fairness.Experimental results show that the proposed adaptive resource allocation algorithm can satisfy the fairness requirement threshold and improve system capacity.