Magnetic　Resonance　Coupling　(MRC)　wireless　power　transfer　(WPT)　is　a　promising　technique　for　portable　devices　and　Internet　of　Things　applications,　which　can　transfer　power　to　energy-constrained　terminals　in　mid-range　with　relatively　high　efficiency.　To　enhance　the　transfer　performance,　by　applying　more　coils　in　transceivers,　multiple-input　single-output　(MISO)　MRC-WPT　system　has　attracted　much　attention　in　recent　years.　In　this　paper,　a　MISO　MRC-WPT　system　with　multiple　transmitters　(TXs)　and　a　single　receiver　(RX)　is　studied　and　its　robust　magnetic　beamforming　problem　is　investigated.　The　optimal　robust　beamforming　design　of　the　currents　of　TXs　is　investigated　to　maximize　the　power　received　by　RX　with　the　mutual　inductance　error　between　TXs　and　RX,　whereas　the　total　power　required　is　less　than　a　certain　value　and　each　TXs　has　a　certain　limited　transmitting　power.　By　using　certain　transformation　techniques,　the　optimization　problem　is　converted　into　a　relaxed　semidefinite　programming　(SDP)　problem　which　can　be　solved　efficiently.　We　further　prove　that　the　solution　of　the　relaxed　SDP　problem　is　always　rank-one,　which　indicates　that　the　relaxation　is　tight,　and　the　optimal　solution　for　the　problem　was　obtained.　Numerical　results　demonstrate　that　the　proposed　beamforming　design　can　achieve　up　to　97%　transfer　efficiency　by　reducing　the　measurement　errors.　©　2019　IOP　Publishing　Ltd.