This study was conducted to research on the size distribution and concentration measurements of slurry droplet by DHM (digital holographic microscopy). The slurry from desulfurization tower was atomized into micron droplets. The ability of DHM to detect micron droplets was studied by simulation. Micro-holographic measurement system of spray field was built, with equivalent CCD (charge-coupled device) pixels being 0.375 mu m. The size distribution of droplets was measured by DHM, showed unimodal distribution from 0.53 to 5.3 mu m, with the peak at about 2.5 mu m. The average particle size was 2.09 mu m. Number concentration of the slurry droplets was also obtained. The concentration of DHM concentrated in the range of 1.5-3 mu m, about 53-1118 mm(-3). Accordingly, the concentration of PDA (phase Doppler anemometer) concentrated in the range of 0.5-5 mu m, about 19-610 mm(-3). The experimental results show that method based on DHM for slurry droplets measurement is feasible. Based on the simulation and experimental research, an on-line measurement system for slurry droplets was designed. (C) 2015 Elsevier Ltd. All rights reserved.