Two types of acousto-optically Q-switched Nd:YVO4/KTA singly resonated optical parametric oscillators are performed. One is signal resonant, where a 1.5 μm wave resonates while a 3.5 μm wave does not. The other is idler resonant, where a 3.5 μm wave resonates while a 1.5 μm wave does not. All the experimental elements are kept the same for these two schemes except for the coatings of the optical parametic oscillator cavity output coupler. For these two kinds of lasers, the output characteristics of the threshold, output power, pulse width, peak power, and beam quality are measured and compared.