Cognitive radio is a new network technology developed in recent years, which focuses on the low utility of spectrum in the wireless communication system. This paper proposes a new algorithm based on the immune clone optimization for unconstrained multi-objective resource allocation in the downlink OFDMA network. We first convert the constraint of data transmission rate proportionality of each user to a proportional objective function, which avoids dealing with the proportion constraint. And an effective coding method is adopted to deal with constraints in subcarrier allocation. Compared with the traditional method, this method can get less code length, which narrows the solution space significantly. Moreover, we use variable multiples clone operation and heuristic mutation operation based on some priori information. Finally, the population is updated in two steps: first, remove some antibodies with high value of proportional objective function; second, choose Pareto dominant solution from the remaining individuals to update the population. Simulation results show that the proposed algorithm can get better performance compared to the previous works.