An improved SM water reducing agent for concrete was synthesized with the low toxic and low cost urea in part replacing melamine.Its technology process and parameters were studied.The effect of the content of water reducing agent on the properties of concrete was investigated.The results indicates that the water reducing agent has positive effect on concrete strength.The rate of water reduced is as high as 35.7%,and the production cost of the water reducing agent is lowered by 22%.Therefore,the water reducing agent has obvious industrial prospect.