Driven by Industry 4.0, collaborative robotic arms share operational space with humans and work together. Safety issues, as a major challenge in human-robot interaction, involve not only the physical aspect of whether the robotic arm itself will harm operator but also the psychological aspect of perceived safety, that is, whether the operator believes the robotic arm is harmless. This article investigates the effect of the motion speed and human-robot distance of a collaborative robotic arm on the operator's perceived safety through experiments. The experiment employs a combination design of independent variables of 3 (speed) × 3 (distance), and quantifies the perceived safety level through subjective scoring. The results indicate that distance has an extremely significant positive correlation with perceived safety, while speed has a significant negative correlation. At medium distances, speed has the most pronounced effect on perceived safety, while at near and far distances, the effect of distance is more dominant. In addition, the impact of robotic arms approaching different key parts of the human body on perceived safety varies, with the head being the most affected and the hands the least. The research provides a reference for optimizing the motion parameters of collaborative robotic arms and enhancing the perceived safety level in HRI, which is of great significance for improving the safety and efficiency of future human-robot collaboration systems.