The invention discloses a client and a method for maintaining a BYOD (Bring Your Own Device) safety. The client comprises a device and user identity authorization module for authorizing the user identity according to the authorizing mode selected by a user using a mobile device from the preset authorizing modes under the condition that the accessed mobile device is determined to be a valid device, and a mobile device managing system for providing management operation for the full life cycle of the mobile device, wherein the management operation includes permanent online message pushing service. With the adoption of the client, authorized people can successfully enter an enterprise system to work, and the circumstance that staff cannot enter an internet network to handle with emergent problem can be avoided.