For the same quantum squeezed field, the squeezing degree is different for the measurement schemes of amplitude-quadrature noise and intensity-difference noise, which is theoretically explained. When the output signal has no loss, the squeezing degrees of intensity-difference noise and amplitude-quadrature noise increase with the increase of gain, but the degree of the former is smaller than that of the latter. When the loss is considered, the squeezing degree of intensity-difference noise is larger than that of amplitude-quadrature noise, which indicates that the squeezing degree of amplitude-quadrature noise is more sensitive to loss.