The invention discloses a system, method and device for dynamically encrypting data based on a key library, which can be used in the field of information security, and the system comprises an inter-application server, a key library server, a plurality of channel application servers and terminals interacting with respective channel application servers, wherein the key library server is used for configuring a data encryption rule for data interacting among different channel application servers and data interacting in the same channel application server, and generating a corresponding encryption program and a key file according to the data encryption rule; the inter-application server is used for downloading a corresponding encryption program and the key file from the key library server according to a data processing request of each channel application server, and encrypting or decrypting application data; and the channel application servers are used for downloading the corresponding encryption program and the key file from the key library server according to the data processing request of the terminal, and encrypting or decrypting the application data. According to the invention, the system safety can be improved.