Level flight is the most common flight state for micro-small fixed-wing Unmanned Aerial Vehicles (UAVs). This chapter introduces the principles for calculating the level flight performance of electrically driven micro-small fixed-wing UAVs and related experiments. First, a kinematic analysis and mathematical modeling of the electric propulsion system for fixed-wing UAVs are conducted. Subsequently, the performance of micro-small fixed-wing UAVs is assessed through a series of experiments—basic, analysis, and design experiments—to enhance the reader’s comprehension of flight principles.