This article makes a comprehensive study of the various effects of separate layer water injection tubular column in the wellbore. On this basis, a mechanical analysis model of the packer is established, In the model, we consider that different tools such as anchoring tools，length accumulators have an effect on the force of packer, and we establish a packer force model, which is much closer to the actual operating conditions, to provide a more practical value for water injection string performance evaluation, construction parameter optimization and design of water injection string.