Data storage has great impacts on the quality of service of cloud computing systems. Storage of massive data in cloud environment is a very challenging problem. In this paper, we propose a multiobjective optimization model for massive data storage in cloud environment, in which the storage cost and reliability are considered simultaneously. The storage cost in the proposed model is considered to be comprised of the cost of storage space occupation, data migration and communication. The storage reliability is composed of data transfer reliability and equipment stability. In order to validate the proposed model, a Particle Swarm Optimization (PSO) algorithm is designed for the proposed multiobjective optimization model. Finally, experiments are made and, the results indicate correctness and validity of the proposed optimization model.