Smart　contract　has　shown　its　potential　in　cutting　down　the　cost　of　administration　through　reshaping　conventional　business　processes　and　in　expanding　the　application　of　blockchain　to　areas　that　are　beyond　the　cryptocurrency.　However,　with　the　rapid　development　and　wide　application　of　smart　contracts,　security　issues　have　become　a　serious　concern　and　have　thus　attracted　widespread　attention.　As　the　result,　a　great　deal　of　effort　has　been　spent　on　improving　and　supporting　secure　development　and　on　the　application　of　smart　contracts　by　introducing　new　and　advanced　vulnerability　detection　and　privacy　protection　techniques　in　recent　years.　There　is　therefore　the　need　for　a　comprehensive　review　of　the　new　development　on　security　enhancement　technologies　of　smart　contracts　for　the　blockchain.　This　paper　provides　a　review　of　the　current　research　status　and　advances　in　smart　contract　security　based　on　related　literature　published　in　recent　years.　Our　review　is　divided　into　six　categories　along　the　line　of　the　technology,　which　includes　symbolic　execution,　abstract　interpretation,　fuzz　testing,　formal　verification,　deep　learning,　and　privacy　enhancement.　A　comparison　of　the　various　tools　and　methods　developed　to　tackle　security　issues　is　provided.　Challenges　in　the　research　of　smart　contract　security　as　well　as　future　directions　are　discussed.　This　paper　intends　to　provide　the　inspiration　and　reference　for　follow-up　research　on　the　security　issues　of　smart　contracts　in　the　blockchain.