By thermo-field dynamics (TFD), we study the quantum fluctuations of charge and magnetic flux of a mesoscopic circuit including resistor, inductor and capacitor (RLC) in coherent states and squeezed states at finite temperature. It is shown that the fluctuations of charge and magnetic flux depend on not only the parameters of the circuit components but also the environmental temperature and squeezing parameters, while the fluctuations don't depend on displacement parameters.