Abstract: Hypercrosslinked polymer (HCP) is a class of microporous organic polymer connected by light elements (C, H, O, and N) through covalent bonds. In order to efficiently adsorb soluble organic dyes in water treatment, here, an ionic HCP (HCP-SO₃Na) was prepared through an efficient Friedel-Crafts reaction from sodium 4-(phenylamino)benzenesulfonate and benzene in the presence of formaldehyde dimethyl acetal and anhydrous FeCl₃. A series of characterizing techniques such as elemental analysis, infrared spectroscopy, N₂ adsorption/desorption analysis, solid-state ¹³C nuclear magnetic resonance spectroscopy and thermogravimetric analysis were employed to characterize the structure and thermal property of the ionic polymer. It was found that HCP-SO₃Na was an amorphous microporous polymer with large specific surface area and high thermostability. The specific surface area and micropore area were 587 m²/g and 411 m²/g, respectively. The adsorption of HCP-SO₃Na for the organic dye of Rhodamine B demonstrated the ―SO₃Na groups distributing uniformly in the polymer could increase the saturation capacity of HCP. The maximum adsorption capacity was up to 431 mg/g. The adsorption process conformed to kinetic pseudo-second-order model and Langmuir model. HCP-SO₃Na can be easily recovered and reused five times without significant loss of activity.