A computer implemented identification method of content metadata for cyber content sharing and governance (MDCCSG), comprising: a central processing system aggregating all the contents within and associated with a content sharing application; generating a content metadata identifier with a uniform format, also referred to as an MDCCSG identifier; wherein the MDCCSG identifier comprises an MDCCSG identifier short code, an MDCCSG property information and a plurality of core content metadata identifier elements, wherein the MDCCSG identifier short code lies in the front of the whole MDCCSG identifier, wherein the MDCCSG identifier short code has a standard length of 32 bytes; wherein different encoding specification formats are adopted respectively for the MDCCSG identifier short code and the MDCCSG property information; in the MDCCSG identifier short code, 32 bytes are fully utilized to define the bit-based content metadata information and a plurality of key fields is described by binary integers, and the description focuses on content semantics and security information; in the MDCCSG property information, a plurality of metadata elements (MDEs) are categorized and collected by metadata set units (MDSUs); wherein flexibility and extensibility of MDCCSG identifiers are ensured by reservation and on-demand extension; wherein the MDCCSG property information closely follows the MDCCSG identifier short code, and contains a plurality of MDSUs; each MDSU contains a plurality of MDEs, and each MDE describing one aspect of property information associated with the content; and the MDCCSG property information contains two compulsory key MDSUs: a description information set unit (DISU) and a management information set unit (MISU), wherein the DISU focuses on describing the basic properties and semantic information of the content; and the MISU focuses on describing important property information related to cyber content management and governance, and wherein the plurality of core content metadata identifier elements are selected, and these core content metadata identifier elements cover semantic description information, trust authentication and security guarantee information of the content, and security energy level identifier elements reflecting content quality properties are created at the same time, and "double-signature mechanism" and "multi-level authentication and registration as well as source tracing and responsibility investigation" functions are supported by adding identify information of each responsibility subject at each level of authentication into a chain of responsibility and generating a signature of whole. a central processing system aggregating all the contents within and associated with a content sharing application; generating a content metadata identifier with a uniform format, also referred to as an MDCCSG identifier; wherein the MDCCSG identifier comprises an MDCCSG identifier short code, an MDCCSG property information and a plurality of core content metadata identifier elements, wherein the MDCCSG identifier short code lies in the front of the whole MDCCSG identifier, wherein the MDCCSG identifier short code has a standard length of 32 bytes; wherein different encoding specification formats are adopted respectively for the MDCCSG identifier short code and the MDCCSG property information; in the MDCCSG identifier short code, 32 bytes are fully utilized to define the bit-based content metadata information and a plurality of key fields is described by binary integers, and the description focuses on content semantics and security information; in the MDCCSG property information, a plurality of metadata elements (MDEs) are categorized and collected by metadata set units (MDSUs); wherein flexibility and extensibility of MDCCSG identifiers are ensured by reservation and on-demand extension; wherein the MDCCSG property information closely follows the MDCCSG identifier short code, and contains a plurality of MDSUs; each MDSU contains a plurality of MDEs, and each MDE describing one aspect of property information associated with the content; and the MDCCSG property information contains two compulsory key MDSUs: a description information set unit (DISU) and a management information set unit (MISU), wherein the DISU focuses on describing the basic properties and semantic information of the content; and the MISU focuses on describing important property information related to cyber content management and governance, and wherein the plurality of core content metadata identifier elements are selected, and these core content metadata identifier elements cover semantic description information, trust authentication and security guarantee information of the content, and security energy level identifier elements reflecting content quality properties are created at the same time, and "double-signature mechanism" and "multi-level authentication and registration as well as source tracing and responsibility investigation" functions are supported by adding identify information of each responsibility subject at each level of authentication into a chain of responsibility and generating a signature of whole.