The invention relates to a password input method and system of a smart lock. The password input method is realized through a first button and a second button, and during password inputting, password input is realized by pressing the first button and the second button respectively according to set passwords. When the set password is a binary password, 0 in the password can be made to correspond to the first button while 1 in the same can be made to correspond to the second button, and input is completed by pressing the first button or the second button corresponding to numbers of the binary password respectively. When the set password is a non-binary password, the non-binary password can be converted into a binary password, and then input is performed according to the password input method of the binary password. By the password input method, number of the buttons used for password input is reduced to greatest extent, energy consumption of the system is lowered greatly, and safety is improved. The password input method and system is suitable for the technical field of the smart lock.