The objective of this study was to investigate the mixing mechanisms in the gas-solid two-phase jet from a fuel rich/lean burner. Laboratory experiments were conducted in a test section with an internal diameter of 0.150 m. Gas-solid jet flow downstream of the fuel rich/lean burner exit was measured using a fiber-optic probe that traversed over the cross section of the jet to obtain the local solid concentration and particle size distribution. The measurement results indicate that the fuel-rich stream and the fuel-lean stream do not mix together soon after leaving the burner, although the two streams are adjacent together, which leads to better ignition and combustion characteristics of the pulverized coal, compared to an ordinary burner. The local high fuel concentration zone can be achieved at the fuel-rich side and the boundaries of the central recirculation zone, resulting in staged combustion to control NO,, emissions.