The soot formation and distribution in coal jet flames were measured using Laser-Induced Incandescence (LII) technique over a wide range of coal mass concentration (C-coal). Experiments were conducted using an entrained-flow burner. The coal particle distributions were visualized using Mie scattering imaging technique and the flame temperature was measured using dual waveband colorimetric thermometry. The results showed that Mie scattering measurement was valid to detect C-coal in the flame under low C-coal conditions, but its accuracy was affected by the soot scattering under high C-coal conditions. At low C-coal's, most coal particles were burned individually and a little amount of soot was formed. When C-coal exceeded a certain value (e.g., C-coal >= 0.60 kg/m(3)), coal flames behaved as "cloud flames" and soot particles were first formed in the outer boundary of the coal jet and then massively produced near the centerline of the coal jet. Most soot particles were oxidized in the downstream. The radial peak soot volume fraction overlapped with that of coal concentration, as the high-temperature zone with low O-2 concentration located very close to the centerline of the coal jet. The soot volume fraction first remarkably increased as C-coal increased, but the trend became less significant when C-coal was high (i.e., >= 1.0 kg/m(3)). The effects of C-coal on the soot formation were attributed to the increase of the volatile amount, expansion of the O-2-deficiency region, and the change of the flame temperature.