An active matrix organic light emitting diode shadow mask assembly includes a shadow mask frame, longitudinal supporting bars, transverse spacer plates, shadow mask plates. The longitudinal supporting bars are disposed on the shadow mask frame at intervals. The transverse spacer plates are disposed on circular rod portions of the longitudinal supporting bars, are supported by the longitudinal supporting bars, are arranged at intervals. The shadow mask plates are disposed on the transverse spacer plates, are supported by the longitudinal supporting bars, parallel the transverse spacer plates. Each transverse spacer plate is located under a gap between adjacent shadow mask plates, contacts the shadow mask plates, covers the gap. The transverse spacer plates directly contacting the shadow mask plates effectively cover the gaps between the shadow mask plates, effectively prevent organic material in a later process from leaking through the shadow mask plates, dropping on to a lower glass substrate.