Chitosan is an important and abundant natural-based polymer, and it has broad applications. However, dissolving chitosan in plain water is a challenge, which mostly limits the biomedical applications of chitosan materials. Herein, we report an ecofriendly dissolution method to obtain a plain water-based chitosan solution for the first time. In this method, dissolving chitosan in ionic liquid followed by overnight freezing at -20 °C and subsequent solvent exchange with plain water at room temperature results in a stable chitosan dispersion in water with nanosize, namely water-based, chitosan pseudosolution. The overall process is ecofriendly. This new method augments the quality and processability of chitosan solutions used in manufacturing and bioprocessing and promotes the biomedical applications of chitosan-based products.