Micro-Doppler (mD) characteristics of the cone space targets (CSTs) have attracted great attention due to the potential for discrimination between targets and decoys. However, current investigations mainly focus on CSTs with perfectly smooth surfaces. This Letter reveals that mD characteristics of CSTs are associated with surface roughness, and the generated data set used for CST recognition should contain rough target samples. Finally, simulation results via the electromagnetic computation verify the correctness of the analysis.