Abstract: This paper investigated the effect of different mass ratios of petcoke / lignite on the static stability of mixture slurries from the macro-scale (phase separation) and mesoscopic scale (particle size) by using Turbiscan LAB stabil- ity analyzer based on multiple light scattering technology. The results showed that when the mass ratio was greater than 7 ∶ 3,the particles in the slurry aggregated and migrated,and the greater the mass ratio,the greater the top layer thick- ness and particle migration rate in 0 -7 d. When the mass ratio was smaller than 7 ∶ 3,the particles aggregated but didn’t settle which caused the increase in average particle size and no visible clear layer on the top of the slurry in 1-7 d. Besides,when the petcoke / lignite mass ratio was larger than 6 ∶ 4,the large particles on the top settled and thus increased the average particle size of the middle part between 0 -90 min,after that the particles in the middle part gradually aggregated and migrated to the bottom of the slurry in 1-7 d. When the mass ratio was smaller than 6 ∶ 4,the average particle size of the middle part remained stable between 0 -90 min,after that the particles in the middle part aggregated and increased the average particle size of the middle part. The order of static stability of slurries pre- pared by different petcoke / lignite mass ratios is that 0 ∶ 10 and 5 ∶ 5 are the best,the other order is 6 ∶ 4,7 ∶ 3,8 ∶ 2,9 ∶ 1,10 ∶ 0. Therefore,from the macro-scale and mesoscopic scale analyses,the mixture slurries with mass ratios greater than 7 ∶ 3 bled moisture,segregated and were unstable because of the coalescence and migration of particles. The mixture slurries with mass ratios equal or smaller than 7 ∶ 3 were stable because of the coalescence and no migra- tion of particles.