In 1997, Z.Huang and R.Ruth proposed a compact laser-electron storage ring (LESR) for electron beamcooling or x-ray generation. Because the laser-wire monitor in the ATF storage ring has worked well and demonstrated the achievement of the world's smallest transverse emittance for a circulating electron beam, we h a ve started the design of a small storage ring with about 10 m circumference and the development of basic technologies for the LESR. In this paper, we describe the design and experimental results of pulse stacking in a 42-cm long optical cavity. Since our primary purpose is demonstrating