A direct-liquid-cooling side-pumped Nd∶YAG multi-disk laser resonator works in quasi-continuous state is presented, in which twenty Nd∶YAG thin disks side-pumped by laser diode arrays are directly cooled by flowing siloxane solution at the end surfaces, while oscillating laser propagates through multiple thin disks and cooling flow layers in Brewster angle. The laminar flow cooling flow field is designed to cool the thin disk. The dissipation capability of the inhomogeneity of the incoming flow is verified by numerical simulation. According to the experiment reported before, a numerical model based on laminar flow is built to measure the cooling ability of the flow field. The experimental result verifies the reliability of numerical model, the thermal safety of the thin disk in laser device is evaluated based on the model. The maximum pulse energy output of 15.7 J is obtained at the pump energy of 49.9 J, corresponding to an optical-optical efficiency of 31.4% and a slope efficiency of 39.2%. The average output power of 1440 W is achieved at the pump pulse width of 250 μs, repetition frequency of 100 Hz, and average pumping energy of 5 kW.