A fan assembly and a fan frame thereof are disclosed. The fan assembly includes a fan frame and an impeller disposed in the fan frame. The fan frame has an air inlet end and an air outlet end, and includes a sidewall, a top portion and a bottom portion. The top portion is disposed close to the air inlet end and connected to one end of the sidewall. The bottom portion is disposed close to the air outlet end and connected to the other end of the sidewall. The bottom portion has at least one silencing structure.