An intracavity KTiOAsO4 (KTA) optical parametric oscillator (OPO) pumped by a laser diode array side-pumped, acousto-optically (AO) Q-switched Nd∶YAG laser is investigated. The output performance of KTA-OPO is tested at different repetition rates and transmissions of the output mirror. Through discussion of the threshold formula of the singly resonant OPO, a plane-concave cavity and a short OPO cavity length are employed to decrease the OPO′s pumping threshold. The parameters of output laser have been measured at different repetition rates and transmissions of the output mirror. When the repetition rates of acousto-optic Q-switch and transmission of output mirror are 4 kHz and 30% respectively, the output peak power of 1570 nm wavelength reaches 5.6×104 W with the pulse width of 2.5 ns. The highest average output power of 560.3 mW is obtained. KTA is a kind of ideal material used to make pocket and portable OPO laser.