The project presents the use of laser and magnetic nanoparticles like iron oxide (Fe3O4) in heavy metal detection in water. In this method, metal Nanomagnets particles result in a magnetic reagent for the rapid removal of heavy metals from solutions or water of magnitude to concentration 0.25wt%. This can be done by measuring the magneto-optical parameters (as a hysteric loop) of the solution as an indication of the change in concentrations of the detected heavy metal. The samples used in this work using the Tigris River water that supported from al-Wathba lab. water projects of the Baghdad water directorate at Baghdad-Iraq. Putting here a study of the effect of graphene and metal oxide such as cobalt and nickel which doped the ferrofluid (iron oxide) /polymer/water (Tigris river water) composite on the magneto-optical properties. The graphene adding had the best result in low threshold magnetic field which was 67mGauss, give the motive to use it in fast sensing and detecting of heavy metal in Tigris river water.