Smoothed particle hydrodynamics (SPH) is a mesh-free numerical approximation technique for simulating various physical problems. A calculation system for transient heat transfer problem by SPH has been improved to deal with various boundary conditions and several model calculations are performed to verify it. As a practical application, the transient temperature field of a brake disk under emergency braking is analyzed. Both solid and ventilated disks are modeled with a moving heat source on the sliding surface. The numerical results show that the temperature sharply fluctuates because of the cyclic loading. Improvement of the calculation model is also discussed.