For　finding　the　relation　between　Martens　hardness　and　Vickers　hardness,　Rockwell　hardness,　tensile　strength,　yield　strength,　research　are　done　on　carbon　alloy　steel　by　experiment,　linear　regression　analysis　and　derivation　of　equation　.Martens　hardness,　Vickers　hardness　and　Rockwell　hardness　of　30　samples　which　contains　3　material　and　10　hardness　levels　are　tested　by　ZHU　2.5　hardness　tester.　On　the　basis　of　180　groups　of　data　obtained　and　analyzed　from　instrumented　indentation　experiments,　mathematic　model　between　Martens　hardness　and　Vickers　hardness　is　established,　by　linear　regression　analysis.　And　mathematic　model　between　Martens　hardness　and　Rockwell　hardness,　tensile　strength,　yield　strength　is　established　on　that　basis.　By　means　of　comparing　the　value　calculated　by　the　mathematic　model　and　obtained　from　tensile　test　using　Electronic　universal　testing　machine,　the　accuracy　of　the　mathematic　model　is　verified.　The　result　show　that　the　relative　error　of　the　four　mathematics　models　which　established　in　this　test　is　below　5%,　and　the　four　mathematics　models　can　be　applied　to　the　practical　engineering　application.