The leakage is serious in the complex formation of a water source project in Huozhou coal-electricity group of Shanxi. Drilling against circulation loss was adopted at first with high construction cost, but it was still difficult to guarantee the project progress. The drilling difficulties in leakage formation were solved by are-foam drilling with high drilling efficiency and low drilling cost. The paper introduced the technology of air-foam drilling in the water source well construction and analyzed the drilling effect and the drilling cost with comparison.