A new Oil-Mineral Aggregate with bentonite and calsium hydroxide and sawdust has been done. Through several dozens of experiments, the coagulation efficiency with bentonite and Ca(OH)2 and sawdust is 94.53%. The functions of bentonite are coagulation, adsorption and emulsification. Calsium hydroxide is a good coagulant-mate, and strengthen the coagulating function of bentonite. It can be used as the source of calcium ions, which can strongly adsorb on both bentonite and oil droplets, and is helpful for the coagulation between bentonite and oil droplets. Sawdust is also very important in the OMA, its fouctions are buoyant, bridge-made and adsorbant.