An optimized algorithm based on multi-objective optimization model is proposed to solve the problem that existing vertical handoff algorithms do not comprehensively consider the impact of users and the network during handoff process. We build Markov chain model of base station to calculate a more accurate network state. Then a multi-objective optimization model is derived to maximize the value of the network state and the user data receiving rate. The multi-objective genetic algorithm NSGA-II is finally employed to turn the model into a final vertical handoffff strategy. The results of the simulation for throughput and blocking rate of networks demonstrate our algorithm significantly increases the system throughput and reduces the blocking rate compared with the existing vertical switching strategy.