An experiment system is set up for studying the characteristics of nonlinear spectrum in quartz single mode fiber. The electro-optical Q-switched pulsed Nd3+∶YAG solid laser, frequency-doubling by potassium titanium oxide phosphate (KTP) crystal, with output pulse width of 10 ns, the maximum peak power of 50 MW, and wavelength of 531.81 nm±0.26 nm, is used to pump the quartz single mode fibers with lengths of 250 m and 500 m. Based on the principle of Malus law, a polarizing plate is used to adjust the output power of the pumping source. Under the stable operation condition, multi stage nonlinear spectra of 250 m and 500 m quartz single mode fibers in the visible region are obtained, while the output powers of pumping sources are 220.6 kW and 170 kW. Based on the principle of the third-order nonlinear effects in quartz single mode fiber, the characteristics of the nonlinear spectra obtained in the experiment are analyzed. Both the theoretical analysis and experimental results indicate that the longer the length of quartz single mode fiber, the larger the relative intensity of nonlinear spectrum and the coupling gain coefficient, and the smaller the energy threshold; while the shorter the length of quartz single mode fiber, the easier the broadening of nonlinear spectra and the generation of scattering additional peak.