Terahertz wave with modulation spectrum is valuable in many fields.Terahertz spectrum has been modulated with a pure-phase liquid crystal spatial light modulator by shaping the femtosecond laser beam profile.In the experiment,terahertz wave is generated by femtosecond laser pulses in mode of Optical Rectification and then its signals are detected by a terahertz time-domain spectroscopy system.Phase maps obtained with the GS algorithm are loaded to get the shaped beam profile.Therefore,Terahertz spectrum has been successfully modulated by changing the detection range and beam profile parameters.Simultaneously,the simulations have been performed with the Fresnel diffraction,and they agree with the experimental results well.The results show that the modulation of the THz spectrum with this method is feasible.