Since the laser beam parameters play crucial role to measure the nonlinear optical parameters of the materials, it is essential to characterize the laser beam spot size, pulse- width and polarization orientation. In the present chapter, the spatial and temporal profile of the ultrashort pulsed laser are investigated by using the knife-edge and the autocorrelation techniques, respectively. In this Chapter we have discussed about the experimental techniques used for the investigations of the nonlinear optical properties of materials. In present chapter the temporal beam profile of laser beam is studied which is followed by the discussion of the results of autocorrelation using fitting tool to extract the values of pulse width. The spatial and temporal beam profile measurements are essential to extract the exact values of the nonlinear susceptibility. The nonlinear optical measurements depend on the laser beam spot size and pulse width. The present chapter includes the experimental data of laser beam radius by using the knife edge and autocorrelation techniques and the nonlinear fitting in Origin lab software.