A　compact　diode-pumped　double　pass　Nd:YVO4　MOPA　laser　system　was　realized.　The　master　oscillator　was　passively　Q　switched　microchip　laser,　and　0.5W　of　average　power　at　20kHz,　2.4ns　of　pulse　duration　was　output　in　TEM　00.　In　order　to　achieve　high　efficiency　and　high　gain　amplification　output,　we　designed　a　compact　structure　to　collimate　the　pump　laser　and　the　seeder　laser.　In　order　to　optimize　the　energy　extraction　and　to　reduce　the　thermal　aberrations,　the　pump　laser　was　collimated　by　a　cylindrical　microlens　in　the　vertical　direction,　and　the　seed　laser　was　collimated　by　focus　lens.　After　double　pass　amplification,　average　output　power　of　12.5W　at　20kHz,　pulse　duration　of　2.5ns　and　M2　of　1.5　was　achieved,　corresponding　to　extraction　efficiency　of　31%.