In this paper, we develop a quasi-cw InGaAs microlens-free diode arrays side-pumped Yb:YAG slab laser which operates at 25Hz. The pump light is transmitted by a lensduct which transmission efficiency is measured about 80%. The laser cavity is plane-concave. We have achieved l6mJ output energy using 8mm X 3mm X 1mm dimension and 5at.% Yb doped crystal with 345mJ input energy of diode arrays which operate in ims pulse mode. For another 8mm X 3mm X 2mm(5at.%) crystal, 8.7mJ output energy is obtained; the beam quality factor M2 values are measured to be 5.83 and 7.66 in the vertical and horizontal directions respectively. The water temperature for cooling diode arrays and crystal are 11.8 ° C and 5 ° C separately.