Due to the increasing temperature in water injection system, scales are sediments that are firmly attached on the metal surface in the industrial equipment. These scales, including calcium and ferric oxide precipitations, can cause heat transfer problems. A non-phosphorus water treatment agent APES/AA/AMPS was synthesized by acrylic acid (AA), ammonium allylpolyethoxy sulphate (APES) and 2-acrylamido-2-methyl propanesulfonic acid (AMPS) with the solution of ammonium persulfate as an initiator. The properties of scale inhibition and dispersion of water treatment agent APES/AA/AMPS were studied by using the commonly used standard test methods. The results showed that APES/AA/AMPS had excellent scale inhibition and dispersion performance. The performance of APES/AA/AMPS on strontium sulfate was 93.3% at the dosage of 9 mg·L−1. When the concentration was 4 mg·L−1, the dispersion of iron oxide was optimal according to the solution transmittance of 13.7%. The morphology and crystallinity changes of strontium sulfate in scanning electron microscopy and X-ray powder diffraction showed that the mechanism of the inhibition on strontium sulfate is adsorption.