Using the linear approximation method, the steady-state mean normalized intensity fluctuation is calculated after input signal in a single-mode laser system driven by pump noise and quantum noise with cross-correlation between the real and imaginary parts. The influences on the steady-state mean normalized intensity fluctuation are analyzed by quantum noise with cross-correlation coefficient between the real and imaginary parts, the intensities of the quantum and pump noise, the amplitude and frequency of input signal and the net gain. It is found that the statistic fluctuation of laser field is smaller in the case of the weaker quantum noise cross-correlation between the real and imaginary parts, smaller noises, far from threshold, smaller amplitude and higher frequency of the signal.