Abstract We observed strong nonlinear absorption in the CdS nanostructure in the range 50-100 nm when irradiant with femtosecond pulsed laser at 800 nm and 120 GW/cm2 irradiance intensity. The repetition rate and average power were 250 kHz and 30 mW respectively. The CdS nanostructures were prepared by chemical spry pyrolysis technique with substrate temperature 300 oC. The structure of the prepared CdS nanostructure was tested and its optical properties were investigated. The structure of the CdS nanostructure was tested with X-Ray diffraction and it was found to be a polycrystalline with recognized peaks oriented in (100), (002), (101), (102), (110), (103), (112), and (004). The measured nonlinear absorption coefficient was found to be about 116 cm/GW which is about ten times higher than the bulk value.