The disclosure relates to an electronic device for generating a mnemonic phrase of a private key and an operation method in the electronic device. The electronic device may comprise a memory, a display module, and at least one processor electrically connected with the memory and the display module. The at least one processor may be configured to generate a private key and a public key, generate a first mnemonic phrase including a designated first number of words based on a structure of the private key, identify a user phrase input by a user, generate a second mnemonic phrase including a second number of words identified based on a security level obtained by analyzing the user phrase, and control the display module to display the generated second mnemonic phrase. Other embodiments are possible.