With　state　space　descriptions,　four　typical　systems　of　mixed　H-two/H-infinity　control　were　defined.　They　are　full　information　system,　full　control　system,　feedforward　disturbance　system　and　output　estimation　system.　Their　controllers　were　designed　to　optimize　the　performance　based　on　a　kind　of　quadratic　stable.　Mixed　H-two/H-infinity　control　system　was　decomposed　into　an　inner　matrix　and　a　mixed　H-two/H-infinity　output　estimation　system.　The　output　feedback　controller　was　deduced　according　to　this　decomposition.　Mixed　H-two/H-infinity　controller　delivered　here　are　analog　to　H-two　and　H-infinity　controller　in　that　they　have　the　same　controller　structure,　the　same　number　of　Riccati　equations　and　similar　Riccati　equations.　The　given　controllers　including　the　H-two　and　H-infinity　cases,　can　be　treated　as　unified　controllers　of　H-two,　H-infinity　and　mixed　H-two/H-infinity　control.　A　simple　example　was　given　to　illustrate　the　proposed　methods.