The invention belongs to the technical field of water treatment, and especially relates to a method for removing thallium pollution in source water of drinking water, which comprises the following steps: a. adjusting the pH value, when the concentration of thallium pollution is not more than 1 microgram/L, adjusting the pH value to 9.0-9.5; when the concentration of thallium pollution is 1 microgram/L-5 microgram/L, adjusting the pH to 9.5-10.0; b. performing preoxidation, allowing Tl+ to be converted into Tl3+ by using potassium permanganate as a preoxidate for thallium, adding 1.5-2.5 mg/L of potassium permanganate, wherein the oxidation time is 20-40 min; c. performing coagulation and sedimentation, adding polyaluminium chloride, allowing Tl3+ to form Tl(OH)3 precipitates, filtering to remove thallium in source water. The invention can adjust the pH value of the source water to an appropriate alkaline range, and promote the conversion of Tl+ to Tl3+, and the thallium removal rate is significantly increased; only oxidant addition is required at the front end of the water treatment process; the investment of capital construction is saved, and no addition of special equipment or structures is required.