A low threshold current density of 2 μm InGaAsSb/AlGaAsSb muti-quantum well (MQW) laser diode with carrier blocking layer (CBL) is demonstrated by simulation and fabrication. The carrier leakage is found to be theoretically suppressed for the devices with CBL. All the laser wafers are grown with a solid source Molecular Beam Epitaxy(MBE) System. Experimental results reveal the samples with CBL exhibits ultra-low threshold current densities of 142 A/cm² and high slope efficiency of 0.158 W/A, which is better than 215 A/cm² and 0.122 W/A achieved in the conventional InGaAsSb/AlGaAsSb LDs at room temperature. This improvement in device performance comes from meticulously designing the carrier blocking layers to increase carrier confinement and injection efficiency.