The present invention provides a method for removing polymer after etching a gate stack structure of high-K gate dielectric/metal gate. The method mainly comprises the following steps: 1): forming a gate stack structure of interface Si2/high-K gate dielectric/metal gate/poly-silicon/hard mask in sequence on a silicon substrate with device isolations formed thereon; 2): forming a resist pattern by the lithography; 3): etching the gate stack structure; and 4): immersing the resultant structure of the step 3) in an etching solution to remove the polymer, wherein the etching solution consists of HF, HCl and water, the ratio of HF by volume is 0.2˜1% and the ratio of HCl by volume is 5˜15%.