A dual-layer linear cross belt sorting system, comprising a package supply table, a sorting loop, a platform, sliding chutes and a scanning device, wherein the sorting loop is of a closed-loop and dual-layer linear conveying structure in a vertical direction, and comprises a plurality of sorting trolleys connected along a single queue, two sets of dual-layer rails formed by connecting bent rails located at two ends and straight rails located at upper and lower layers to each other by means of internal welding, and a driving component; characterized in that the sorting loop further comprises a tensioning component, wherein the driving component and the tensioning component constitute a transmission structure of the sorting loop and are located at two ends of the loop respectively; and the dual-layer rails distributed along the two sides of the sorting trolleys of the single queue and synchronous belts connected between the driving component and the tensioning component jointly constitute the vertical, dual-layer linear and closed-loop conveying mechanism of the sorting loop, wherein the driving component has a first driving disc assembly and a second driving disc assembly which are wound from the same side end and drive the two sets of synchronous belts; the tensioning component has a first driven disc assembly and a second driven disc assembly which are wound from the same side end and drive the two sets of synchronous belts; the first driving disc assembly is staggered relative to the bent rail on the same side, and a vertical circle center of the first driving disc assembly coincides with a circle center of a vertical circle where the bent rail on the other side of the sorting trolleys is located; the second driving disc assembly is staggered relative to the bent rail on the same side, and a vertical circle center of the second driving disc assembly coincides with a circle center of a vertical circle where the bent rail on the other side of the sorting trolleys is located; and the first driven disc assembly is staggered relative to the bent rail on the same side, and a vertical circle center of the first driven disc assembly coincides with a circle center of a vertical circle where the bent rail on the other side of the sorting trolleys is located; the second driven disc assembly is staggered relative to the bent rail on the same side, and a vertical circle center of the second driven disc assembly coincides with a circle center of a vertical circle where the bent rail on the other side of the sorting trolleys is located. the sorting loop further comprises a tensioning component, wherein the driving component and the tensioning component constitute a transmission structure of the sorting loop and are located at two ends of the loop respectively; and the dual-layer rails distributed along the two sides of the sorting trolleys of the single queue and synchronous belts connected between the driving component and the tensioning component jointly constitute the vertical, dual-layer linear and closed-loop conveying mechanism of the sorting loop, wherein the driving component has a first driving disc assembly and a second driving disc assembly which are wound from the same side end and drive the two sets of synchronous belts; the tensioning component has a first driven disc assembly and a second driven disc assembly which are wound from the same side end and drive the two sets of synchronous belts; the first driving disc assembly is staggered relative to the bent rail on the same side, and a vertical circle center of the first driving disc assembly coincides with a circle center of a vertical circle where the bent rail on the other side of the sorting trolleys is located; the second driving disc assembly is staggered relative to the bent rail on the same side, and a vertical circle center of the second driving disc assembly coincides with a circle center of a vertical circle where the bent rail on the other side of the sorting trolleys is located; and the first driven disc assembly is staggered relative to the bent rail on the same side, and a vertical circle center of the first driven disc assembly coincides with a circle center of a vertical circle where the bent rail on the other side of the sorting trolleys is located; the second driven disc assembly is staggered relative to the bent rail on the same side, and a vertical circle center of the second driven disc assembly coincides with a circle center of a vertical circle where the bent rail on the other side of the sorting trolleys is located.