In　the　present　paper　the　results　from　theoretical　solutions　of　multiple　cracks　are　compared　with　the　experimental.　The　synthetic　modulus　of　deformation　and　the　synthetic　Poisson＇s　ratio　of　a　multiple-crack　body　were　studied.　The　existence　of　series　cracks　in　the　material　and　the　behaviours　of　cracks　during　different　loading　have　a　very　important　effect　on　the　macro-mechanical　properties　of　material.