This paper presents two multiwavelength methods to improve the accuracy of a DIAL system for measuring SO₂ in the lower atmosphere: a dual-DIAL method using three or four wavelengths, and a curvefitting method using five wavelengths. By the selection of appropriate wavelengths, these methods can eliminate the effects of ozone and aerosols. Since there is no significant difference in accuracy between the four wavelength dual-DIAL and curvefit methods, the former is advantageous for SO₂ detection in view of the measurement and data processing speeds.