Abstract: An optimization program for the operating parameters and efficiency of gyrom-onotron based on the optimum control theory has been discussed in this paper. In this program we employ the orbit theory of gyromonotron and adopt a slowly varying static magnetic field to enhance the interaction efficiency. An integrated optimum control problem comprising the state equations, the conjugate equations, the objective functional and the functional gradient is worked on in detail in a slowly time-varying coordinate system. The above optimization problem is numerically solved using Goldfarb's method (BQFS method) for fixed parameters V₀ (beam voltage) and a (ratio of initial transverse velocity to parallel velocity) to obtain the optimum operation parameters A, N_λ, μ, b₁, b₂, and optimum interaction efficiency η_e. Then the product of QI can be calculated. A large number of optimized data which can be used in design of gyromonotron are provided and some remarks on this theoretical analysis are given.