A laser-diode (LD) pumped Nd:YAG compact laser system that is capable of generating 1064-nm, 1-J output pulses in several tens of nanoseconds pulse duration at 300-Hz repetition rate (300-W average power) was developed. A concept of this laser system is based on a ubiquitous machine that is easy to transport and process test rapidly in laboratory. A footprint is 1.2-m in width and 2.4-m in length. This laser system is a master-oscillator power-amplifier (MOPA) architecture that allows for increasing the output energy by adding amplifiers. It consisted of an acousto-optic Qswitched Nd:YAG oscillator, a ϕ3-mm Nd:YAG preamplifier and three ϕ12-mm Nd:YAG main amplifiers. The oscillator generated 6-mJ pulse energy at 37-ns pulse duration that could be adjusted by changing the cavity length. The main amplifier had a small-signal gain (SSG) of 9 by laser diodes (LDs) pumping with maximum 27-kW peak power. The beam size and divergence were adjusted to compensate for thermal lens effect in each amplifier. Single-pass amplification by three main amplifiers increased the pulse energy to 1 J. The pumping repetition rate was fixed to obtain thermally stable condition. However, the output repetition rate is variable from single shot to 300 Hz by controlling the oscillator for the experiment usability.