The present invention provides a method for groundwater remediation using sustained-release persulfate tablets, which is to synthesize the persulfate and cellulose with specific ratio to form a remediated tablet, and the manufacturing process is operated under the specific pressure. In the composition of the tablet, the persulfate is used as an oxidant while the cellulose is used as a coating agent. The compound of the tablet is coated with the cellulose to slow the releasing rate of the compound and improve the releasing time of the persulfate in the water.