We have demonstrated direct and stable flat-top beam emission from a passively Q-switched microchip laser, featuring an intracavity spot-defect for mode selecting. By adjusting the distance between the focusing lens and the microchip laser, the Gaussian, flat-top, and doughnut-shaped mode can be achieved separately. The flat-top mode is obtained due to the equally weighted superposition of Gaussian and doughnut-shaped mode. By using the self-injection seeding technique, the timing jitter of these three kinds of mode can be reduced effectively.