Both　polar　codes　and　physical　network　coding　(PNC)　are　promising　techniques　to　achieve　low-latency　and　high-rate　transmission　in　5G　communications.　In　this　letter,　we　investigate　a　joint　polar-coded　PNC　system　over　a　wireless　two-way　relay　channel　(TWRC).　By　exploiting　the　nature　of　PNC,　we　then　propose　two　successive　cancellation　list　(SCL)　decoding　schemes　for　the　polar-coded　PNC　system,　XOR-based　conventional　SCL　(XOR-SCL)　and　joint　decoding　of　PNC　and　SCL　decoding　(JPSCL),　where　message　update　rules　are　derived　for　odd　and　even　channels.　Simulation　results　demonstrate　that　JPSCL　outperforms　XOR-SCL　over　both　AWGN　and　Rayleigh　fading　channels.　In　particular,　JPSCL　achieves　a　small　bit　error　rate　gap,　i.e.,　within　1　dB　at　rate　of　2/5,　from　SCL　in　the　polar-coded　point-to-point　system　at　BER　of　10(-5).