This paper presents a solution procedure of surveillance parameter optimization to achieve minimum radar load while ensuring desired one-off and cumulative probabilities of detection in a multi-function phased array radar. The key approach is to convert the nonlinear optimization on four search parameters - beam width, beam spacing ratio, dwell time, and frame time - into a scalar optimization on signal-to-noise ratio by a semi-analytic procedure based on subproblem decomposition, which improves computational efficiency of the optimization process as well as facilitates physical interpretation of the optimized parameters. The efficacy of the proposed solution approach is verified with theoretical analysis and numerical case study on an airborne phased array radar.