We present echofriendly laser ablation technique of Synthesizing iron oxide nanoparticle in pure water and discuss the impact of laser energy on the size, shape and morphology of the nanoparticle. The synthesized nanoparticle was characterized by UV/Visible absorption spectroscopy and morphological study was performed by scanning electron microscope (SEM). Intensity and wave length of the absorption peak of the colloidal nanoparticle prepared in water are dependent on the laser energy. Red-shift in the absorption band was observed at increasing laser energy. The intensity of absorption peak also changed when ablating laser energy was increased. The spherical natures of the nanoparticle is lost as the laser energy gradually increases and finally triangular shaped structures is observed as the laser energy increases from 9.3 mJ to 75 mJ.