To　shorten　the　length　of　the　pulse-forming　line　(PFL)　and　generate　pulses　with　good　flat-top　quality,　a　5-GW　Tesla-type　pulse　generator　based　on　a　mixed　PFL　is　developed　in　this　paper　to　produce　intense　electron　beams　and　generate　high-power　microwaves　(HPMs).　The　mixed　PFL　is　composed　of　a　coaxial　PFL　and　a　multistage　series　annular　PFL,　which,　in　turn,　consists　of　18　coaxial-output　capacitor-loaded　annular　PFL　modules　in　series.　The　generator　can　produce　quasi-square　electrical　pulses　with　a　width　of　43　ns　and　a　peak　power　of　5　GW　on　a　matched　load.　In　experiments　where　it　is　used　to　drive　a　relative　backward-wave　oscillator　to　generate　HPMs,　the　results　show　that　the　HPM　frequency　is　16.15　GHz　and　the　power　is　1.06　GW　with　an　efficiency　of　25%　when　the　voltage　of　the　diode　is　620　kV　and　the　beam　current　is　6.9　kA.　©　2020　Author(s).