The invention discloses a stable white-light organic thin-film electroluminescent device with bipolar mixed spacer layers, and a preparation method thereof. The stable white-light organic thin-film electroluminescent device comprises a substrate, an anode, a hole injection layer, a hole transport layer, an orange-light ultrathin light emitting layer, a bipolar mixed spacer layer, a green-light ultrathin light emitting layer, a bipolar mixed spacer layer, a blue-light ultrathin light emitting layer, an electron transmission layer, an electron injection layer and a cathode which are sequentiallystacked. The stable white-light organic thin-film electroluminescent device does not use a doped illuminating system, avoids the problems that the doping concentration is difficult to control and doping is repeatedly performed, simplifies the process flow, saves materials, and reduces cost. According to the preparation method, the luminescent materials of different colors are prepared into different regions of the same bipolar mixed spacer layer, and the problem of driving voltage increases caused by a multiple light emitting layer structure is solved. The energy transfer system in the stablewhite-light organic thin-film electroluminescent device is effectively constructed and controlled, and finally the multi-spectral white-light organic thin-film electroluminescent device with stable spectra is obtained.