A real-time imaging system based on a compact terahertz laser is constructed by employing one off-axis parabolic mirror and one silicon lens. Terahertz imaging of water, water stains, leaf veins, human hairs, and metal wire is demonstrated. An imaging resolution of 68 µm is achieved. The experiments show that this compact and simplified imaging system is suitable for penetration demonstration of terahertz light, water distribution measurement, and imaging analysis of thin samples.