A　66.4W　LD-pumped　Nd:YAG　MOPA　all-solid-state　bidirectional　voltage　supplied　Q-switched　nanosecond　laser　was　demonstrated.　Fundamental　mode　1064nm　in　center　wavelength　with　pulse　width　tunable　from　5ns　to　18ns　was　obtained　at　the　repetition　rate　of　500Hz.　The　oscillator　was　scaled　up　to　66.4W　through　multistage　Nd:YAG　amplifiers　at　the　pulse　width　of　6　ns　with　the　divergent　angle　less　than　1.7mrad.　The　corresponding　peak　power　reached　22.1MW　for　each　single　pulse,　and　the　single　pulse　energy　fluctuation　was　less　than　3.94%　in　1　hour　operation.