An improved all-fiber-connected optical modulation setup has been established for the direct measurement of the intrinsic frequency response of semiconductor lasers. The analytical expression of the dynamic response of high-speed semiconductor lasers has been deduced from the rate equations. The measurements have been made with a calibrated vector network analyzer (VNA), and the effects of the pump laser and photodetector have been removed from the measured data using direct-subtracting method and mutual-subtracting method. The accurate intrinsic frequency response of semiconductor lasers can therefore be obtained. The experiment shows that the results obtained using these two methods agree well as expected. It is not only an improvement of extracted data, but also an extension to the range of measurable frequency.