To　get　the　actual　value　and　distribution　pattern　of　earth　pressure　acting　on　the　supporting　structures　in　deep　pit,　a　method　for　earth　pressure　back　analysis　using　in-situ　monitoring　data　is　proposed.　The　procedures　and　formulas　for　back　analysis　of　earth　pressure　have　been　derived.　Utilizing　the　in-situ　monitoring　data　from　a　typical　project　in　Beijing,　the　lateral　earth　pressure　has　been　obtained.　Comparison　between　the　measured　and　the　calculated　values　of　earth　pressure　shows　that　the　proposed　method　is　reasonable　and　reliable.　Furthermore,　numerical　simulation　with　FLAC　has　been　conducted;　and　the　comparisons　among　the　measured,　the　calculated　and　the　simulated　values　of　moment　in　retaining　piles　show　this　method　is　reasonable　and　meaningful.　The　reliability　of　the　method　has　been　verified　more.