The invention relates to a permafrost region expressway flaky and blocky stone ventilation roadbed and a construction method thereof. The construction safety and the service life are severely influenced caused by the lengthways cracking of the roadbed, the roadbed size effect under the asphaltpavement and the like because of the hot melting and the sinking of the permafrost roadbed. The construction method comprises the following steps of: impacting, laminating and filling 30cm of lower gravel cushion layer at a soil arching base; impacting and laminating the lower gravel cushion layer under the ground line; building a flaky and blocky stone layer with the thickness of 0.9m-1.5m on the lower gravel cushion layer; flattening the upper part of the flaky and blocky stone layer by a macadam transition layer with the thickness of 20cm; filling an upper gravel cushion layer with the thickness of 30cm; paving a water-permeable geotextile between the upper gravel cushion layer and the macadam transition layer; distributing a geogrid which is made from the plastic steel at the upper part of the upper gravel cushion layer; and compacting by a heavy type vibratory roller layer by layer. Therefore, the melting of the permafrost roadbed and the uneven deforming of the permafrost roadbed can be reduced, the influence of the climate warming and the human engineering activity to the permafrost roadbed characteristic can be reduced, and the safety and the flaky and blocky stone stability of the roadbed structure can be improved.