A　causal　algebra　and　its　application　to　high　energy　physics　is　proposed.　Firstly　on　the　basis　of　quantitative　causal　principle,　we　propose　both　a　causal　algebra　and　a　causal　decomposition　algebra.　Using　the　causal　decomposition　algebra,　the　associative　law　and　the　identity　are　deduced,　and　it　is　inferred　that　the　causal　decomposition　algebra　naturally　contains　the　structures　of　group.　Furthermore,　the　applications　of　the　new　algebraic　systems　are　given　in　high　energy　physics.　We　find　that　the　reactions　of　particles　of　high　energy　belonging　neither　to　the　group　nor　to　the　ring,　and　the　causal　algebra　and　the　causal　decomposition　algebra　are　rigorous　tools　exactly　describing　real　reactions　of　particle　physics.　A　general　unified　expression　(　with　multiplicative　or　additive　property)　of　different　quantities　of　interactions　between　different　particles　is　obtained.　Using　the　representation　of　the　causal　algebra　and　supersymmetric　R　number,　the　supersymmetric　P-R　=　(-1)(R)　invariance　of　multiplying　property　in　the　reactions　of　containing　supersymmetric　particles　is　obtained.　Furthermore,　a　symmetric　relation　between　any　components　of　electronic　spin　is　obtained,　with　the　help　of　which　one　can　simplify　the　calculation　of　interactions　of　many　electrons.　The　reciprocal　eliminable　condition　to　define　general　inverse　elements　is　used,　which　may　renew　the　definition　of　the　group　and　make　the　number　of　axioms　of　group　reduced　to　three　by　eliminating　a　superabundant　definition.