The principle and method of designing double-side transversely-pumped high-power pulsed dye laser amplifier are presented based on the simplified rate equation of transversely-pumped dye laser amplifier at quasi-steady state. A double-side transversely pumped dye laser amplifier with 50 W output power was developed based on the results of physical design of high power pulsed dye laser amplifier. The experimental study has been performed on this dye laser amplifier pumped by copper vapor laser (CVL). The output power of the amplifier was over 52 W, and the extraction efficiency was up to 41%. The experimental results of the extraction efficiency and output power related to the laser wavelength, input dye laser power and pump beam′s temporal and spatial performance have been given. Furthermore, the influence of dye solution concentration on the beam quality of the double-side transversely-pumped dye laser amplifier has been discussed.