The conventional multi-loop control of a boost converter needs a current sampling circuit to detect the inductor current. Sensorless multi-loop control reduces the cost, size and weight of the power conversion system. The Luenberger observer (LO) is widely used to estimate the inductor current for the sensorless control of a switching converter. However, the design of the LO based sensorless multi-loop control has not been well presented by far. In this paper, a closed-loop characteristics evaluation method is proposed to design a LO based sensorless multi-loop control for boost converters. Simulations show the closed-loop characteristics evaluations. Practical experiments on a digital processor confirm the simulations.