We　present　a　high　compact　structure　laser　diode　(LD)　side-pumped　all-solid-state　Q-switched　master　oscillator　power　amplifier　(MOPA)　laser　system　with　high　beam　quality.　Bidirectional　voltage-supplied　Q-switched　and　MOPA　technologies　were　introduced　in　the　design.　An　in-center　wavelength　of　1064　nm　with　pulse　width　adjustability　from　5　to　18　ns　was　obtained　at　the　repetition　rate　of　500　Hz.　Through　multistage　Nd:YAG　amplifiers　at　the　pulse　width　of　6　ns,　the　oscillator　was　scaled　up　to　145　W　and　the　corresponding　peak　power　reached　48.3　MW　with　single　pulse　energy　fluctuation　less　than　0.45%　in　1　h　operation.　(C)　2013　Society　of　Photo-Optical　Instrumentation　Engineers　(SPIE)　[DOI:　10.1117/1.OE.52.2.024202]