An etchant composition, a tackifier, an alkaline solution, a method of removing polyimide and an etching process are provided. The etchant composition includes a tackifier (A) and an alkaline solution (B). The tackifier (A) includes a resin containing a hydroxyl group (a), a surfactant (b) and a first solvent (c1). The alkaline solution (B) includes an alkaline compound (d) and a second solvent (c2).