We present a simple design method for the hole-slot-type cavity magnetron. Our design model includes all principal parts of magnetron, namely, the cathode, the resonant system, the interaction space, and the magnetic circuit. We first find structural, electrical, and magnetic parameters using empirical formulas. Then, using empirical values as initial guesses, we build and simulate the 3-D model of magnetron in CST Particle Studio. In CST, we show that the eigenmode solver is essential for proper mode excitation; then, we use particle tracking and particle-in-cell simulations for the desired magnetron operation. For a fast convergent result, we study the impact of design parameters on the magnetron performance. We apply this design procedure to an X-band hole-slot-type magnetron with eight resonators. We believe that our method provides designers a simple, fast, and reliable tool for hole-slot-type magnetron design.