In　this　paper,　a　focused　detection　system　for　X-ray　pulsar-based　Navigation　(XNAV)　is　designed　based　on　Silicon　Drift　Detector　(SDD).　The　detector　electronics　mainly　adopts　the　digital　trapezoidal　shaping　method　to　measure　the　Times-Of-Arrival　(TOAs)　and　energy　of　photons.　The　time　measurement　accuracy　is　better　than　500ns.　The　energy　resolution　is　191eV　at　8.05keV,　and　the　maximum　count　rate　is　500kcps　between　1　and　12keV.　In　the　semi-physical　simulation　experiment,　the　filtering　of　noise　photons　by　energy　discrimination　significantly　improves　the　correlation　degree　between　the　cumulative　pulse　profile　and　the　standard　profile.