The invention relates to a steel truss assembly system which comprises a steel truss, a ground, a structural column, an installation point, an aerial assembly device and a hoisting system. The structural column is arranged on the ground, the installation point is arranged at the top end of the structural column, and the two ends of the steel truss are arranged at the installation point; the hoisting system comprises a hoisting point support frame, a steel rope, a hoisting hook and a crane, wherein the hoisting point support frame is arranged on the steel truss, the hoisting point support frameis connected with the steel rope, the crane is arranged in a ground operation area, and the crane is connected with the steel rope through the hoisting hook; and the aerial assembly device is arranged below a steel truss sectional splicing position. The steel truss assembly system has the beneficial effects that a track type adjustable vertical rod is adopted to support an assembly jig, the widthand the height of the assembly jig can be accurately adjusted, the system is suitable for assembling steel trusses with different forms and sizes, the installation precision of the steel trusses is improved, the engineering quality is improved, the construction progress is accelerated, construction is easy and convenient, and safety and reliability are realized.