In our experiment, the preinscribing method replaces the traditional preload monitoring method. The other error is reduced by directly monitoring the wavelength change; the FBG inscribing wavelength precise controlling is realized. We inscribed six FBGs with different wavelengths; the actual inscribed value of the center wavelength is in good agreement with the target value. The mean error of the FBG center wavelength is 0.007 nm and the standard deviation of error is 0.029 nm. Thus, our method proves to be simple, stable, and reliable, and it can effectively improve FBG center wavelength writing accuracy.