An external tubular linear permanent magnet generator (ETLPMG) is proposed for direct drive wave energy conversion. ETLPMG with quasi-Halbach array is larger in the air gap magnetic flux density than the internal and radial magnetisation one. An assistant tooth and fractional slot are implemented to decrease the detent force. The power density of ETLPMG is about 7–8 times for that of the internal one and the efficiency reached 90.03% at 18 Ω condition. The characteristics of the ETLPMG are analysed with a finite element analysis. Finally, a prototype is manufactured to verify the simulation results by some experiment tests.