In this paper, the sintering behavior and microstructural evolution of as-prepared monodispersed β-Ga2O3 micro-ellipsoid particles (E-G), β-Ga2O3 micro-rods particles (R-G) and as-received commercial β-Ga2O3 particles (C-G) were investigated. The XRD analysis showed that the main peak (−202) of E-G and R-G ceramics sintered at elevated temperature, ascribed to the lowest surface energy of the (−202) crystal surface. The in-situ high temperature optical dilatometer analysis revealed that, compared with C-G, the monodispersed E-G and R-G had higher sintering activity with a more uniform particle size and a smaller aspect ratio and the densification temperature of as-prepared β-Ga2O3 was reduced by over 100°C. The highest density of E-G, R-G and C-G ceramics were 5.96g/cm3 sintered at 1400°C, 5.98g/cm3 sintered at 1450°C and 5.89g/cm3 sintered at 1550°C, respectively. Differential densification and subsequent separation of the pores from the boundaries led to the lower density of C-G ceramics. Due to a higher sintering activity, E-G and R-G ceramics had larger grains than those of C-G ceramics sintered at the same temperature. Furthermore, the sintering temperature had an important effect on the microstructure and weight losses of sintered Ga2O3 ceramics. Finally, the high-density target obtained using Ga2O3 particles with uniform size as the raw materials exhibited promising industrial applications for optoelectronic devices.