This paper reports the generation of high power quasi-continuous wave (Q-CW) red laser radiation by frequency-doubling a Nd∶YAG (Nd∶Y3Al5O12) laser operating at wavelength near 1.3 μm with a KTP (KTiPO4) crystal (type Ⅱ phase match, θ=59.9°, φ=0°). The laser, with plane-concave cavity structure, is employing a high power CW pump module comprised a Nd∶YAG rod side-pumped by thirty 20 W laser diode arrays (LDAs) of a triangle radial geometry, and an acousto-optic Q-switch which results in the laser high repeated Q-CW output. The laser output characteristics of fundamental and frequency-doubled wavelengths involving powers and spectra have been studied. The highest power of the quasi-CW red laser is 8.1 W, achieved at 453 W pump power of LD. The value of M2 and the distribution figure of red beam at 8.1 W output power are given in the paper.