The　mechanical　properties　and　failure　mechanism　of　lightweight　aggregate　concrete　(LWAC)　is　a　hot　topic　in　the　engineering　field,　and　the　relationship　between　its　microstructure　and　macroscopic　mechanical　properties　is　also　a　frontier　research　topic　in　the　academic　field.　In　this　study,　the　image　processing　technology　is　used　to　establish　a　micro-structure　model　of　lightweight　aggregate　concrete.　Through　the　information　extraction　and　processing　of　the　section　image　of　actual　light　aggregate　concrete　specimens,　the　mesostructural　model　of　light　aggregate　concrete　with　real　aggregate　characteristics　is　established.　The　numerical　simulation　of　uniaxial　tensile　test,　uniaxial　compression　test　and　three-point　bending　test　of　lightweight　aggregate　concrete　are　carried　out　using　a　new　finite　element　method-the　base　force　element　method　respectively.　Firstly,　the　image　processing　technology　is　used　to　produce　beam　specimens,　uniaxial　compression　specimens　and　uniaxial　tensile　specimens　of　light　aggregate　concrete,　which　can　better　simulate　the　aggregate　shape　and　random　distribution　of　real　light　aggregate　concrete.　Secondly,　the　three-point　bending　test　is　numerically　simulated.　Thirdly,　the　uniaxial　compression　specimen　generated　by　image　processing　technology　is　numerically　simulated.　Fourth,　the　uniaxial　tensile　specimen　generated　by　image　processing　technology　is　numerically　simulated.　The　mechanical　behavior　and　damage　mode　of　the　specimen　during　loading　were　analyzed.　The　results　of　numerical　simulation　are　compared　and　analyzed　with　those　of　relevant　experiments.　The　feasibility　and　correctness　of　the　micromodel　established　in　this　study　for　analyzing　the　micromechanics　of　lightweight　aggregate　concrete　materials　are　verified.　Image　processing　technology　has　a　broad　application　prospect　in　the　field　of　concrete　mesoscopic　damage　analysis.