An intracavity KTiOPO 4 (KTP) frequency doubling laser emitting at 561 nm is achieved within a diode side-pumped acousto-optically Q-switched Nd:YAG laser. A compact convex-flat straight cavity is employed to achieve the compact configuration, where coatings are specially designed to suppress unwanted lines. At the pump power of 147 W and the pulse repetition rate of 10 kHz, the output power of 8.1 W was obtained at 561 nm. The corresponding optical-to-optical conversion efficiency is 5.5%. The pulse width of a 561 nm wave is 210 ns. The M 2 factors are measured to be 15.5 and 17.5 in the horizontal and vertical directions respectively.