This paper presents an approach to the design of a thermal stabilization system for the optoelectronic equipment (OEE) operating at low ambient temperatures and based on a relay controller. The main goal of the design procedure is minimization of the amount of the warm-up time tw and the number of heater switchings. The constraints applied to the spatial gradients of the design elements should be taken into account in order to limit deformation of the OEE design. Since these constraints are applied only to the system state variables, the controller parameters' constraints cannot be explicitly formulated. We use the electro-thermal model for the object control in the design procedure. This model describes adequately the energy balance of the thermal processes and thermal responses TaO), TB(t) in points A, B of the OEE design. Model approximation error is critical for the controller, which uses differential signal TA^(t) = Ta(0 - T](t) to fulfill the condition tw - min. Experiments with physical models show that this error can be significantly decreased by introduction of additional poles of the transfer function. Pareto optimal relay controller parameters are determined as a result of solving the vector optimization problem, which minimizes the amount of OEE warm-up time and the number of the heater switchings. Experiments confirm the compliance of all the constraints applied to the temperature gradients of OEE design elements. The proposed technique was used for designing of the thermal stabilization system for a diode-pumped solid-state laser.