To　solve　the　problem　of　inaccurate　estimation　of　propagation　method　(PM)　under　low　signal-to-noise　ratio　(SNR)　and　small　snapshots,which　exists　in　the　process　of　two-dimensional　L-shaped　array　parameter　estimation,　an　improved　PM　in　two-dimentional　direction　of　arrival　(DOA)　estimation　algorithm　based　on　array　expansion　was　proposed　in　this　paper.　In　this　method,　the　covariance　matrix　was　extended　and　rearranged　by　using　the　rotation　invariance　characteristics　and　the　propagator　was　got　through　the　covariance　matrix.Then　the　relationship　was　obtained　between　the　block　propagation　operator　and　the　array　flow　pattern　by　using　the　extending　covariance　matrix,which　further　improves　the　estimation　performance.　Then　the　elevation　angle　was　matched　with　the　azimuth　angle　through　fast　pairing　method,　in　turn,　an　accurate　estimation　of　the　angle　was　achieved.　Compared　with　the　existing　algorithms,　the　proposed　method　is　more　suitable,　accurate　and　practicable,　especially　in　the　case　of　low　SNR　and　small　snapshots.Simulation　experiments　show　that　the　proposed　algorithm　has　better　two-dimentional　DOA　estimation　performance.　©　2019,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.