A network monitoring apparatus, and a remote encryption and remote activation method, device and system thereof are provided. The method includes the following steps: receiving an encrypted activation password sent by a client terminal; decrypting the encrypted activation password to obtain an original activation password; determining whether the original activation password meets a predetermined password strength requirement; when the original activation password meets the predetermined password strength requirement, activating the network monitoring apparatus and setting the original activation password as an administrator password; and returning information indicating that the network monitoring apparatus is successfully activated to the client terminal. A network monitoring apparatus, an encryption method of a network monitoring apparatus based on a client terminal, a client terminal, and a remote activation system based on a network monitoring apparatus are also provided. The present disclosure combines an asymmetric encryption mode and a symmetric encryption mode, so as to enhance a security of an activation process.