The invention relates to the technical field of road construction engineering of a perenial frozen soil area, in particular to an 'L'-shaped retaining wall, a construction method and a test method thereof. The invention provides the 'L'-shaped retaining wall, the construction method and the test method thereof, which overcome the defects in the prior art. The 'L'-shaped retaining wall adopts the following technical proposal in order to overcome the detects in the prior art: the 'L'-shaped retaining wall comprises a rectangular pedestal, wherein a supporting wall is arranged on the upper part of the rectangular pedestal and is narrow on the upper part and wide on the lower part; one side face of the supporting wall is a vertical plane and the other side face of the supporting wall is an inclined plane; and the supporting wall is arranged inclined to one side of the rectangular pedestal. The construction method for the L'-shaped retaining wall comprises the following steps in turn: (a) preparatory treatment; (b) excavation; (c) lifting and backfilling; and (d) grading. The test method for the L'-shaped retaining wall is to arrange a plurality of earth pressure boxes on one side of the vertical plane, wherein the earth pressure boxes are overlapped from the top down in turn.