The invention relates to an anti-pollution agent. The anti-pollution agent comprises the following components by weight: 100 parts of water, 20-70 parts of a chelating agent, and 0.1-3 parts of a pH conditioning agent. The invention also relates to a preparation method of the anti-pollution agent. The method comprises the following steps: 1) dissolving the chelating agent in water, 2) using the pH conditioning agent for adjusting the pH value of a chelating agent aqueous solution; and 3) heating a reaction system obtained in the step 2) and aging the system, and filtering the product. The invention also relates to a water-based insulating liquid. The insulating liquid comprises the following components by weight: 100 parts of water, 1-30 parts of a suspension stabilizing agent, 0-300 parts of a density conditioning agent, and 0.1-10 parts of the anti-pollution agent, and optionally 0.1-1 part of an antifoaming agent; wherein the anti-pollution agent is the anti-pollution agent provided by the invention. The invention also relates to a preparation method of the water-based insulating liquid and an application thereof.