The invention discloses a method for preparing high-strength chitosan hydrogel through thermal gelation-nearly neutral water bath. The method comprises the following steps: preparing 0.5-8.0wt% of chitosan, 4.0-6.0wt% of lithium hydroxide, 4.0-8.0wt% of potassium hydroxide and water, mixing and dissolving the components, freezing, thawing, filtering, centrifuging and defoaming the mixture, injecting the mixture into a gel preparation mould to carry out thermal gelation, and then, demolding and soaking in water, removing the alkaline hydroxide in nearly neutral water bath by utilizing phenolphthalein or bromothymol blue as an indicator, and removing the neutral salt and the indicator by using deionized water, thus obtaining the high-strength chitosan hydrogel.