In this study, we demonstrated that the widely used cold atmospheric plasma (CAP) jet could significantly inhibit the growth of melanoma cells using a contactless treatment method, The flow rate of helium gas was a key operational parameter to modulate electromagnetic (EM) effect on melanoma cells. Metal sheets with different sizes could be used as a strategy to control the strength of EM effect. More attractive, the EM effect from CAP could penetrate glass/polystyrene barriers as thick as 7 mm. All these discoveries presented the profound non-invasive nature of a physically based CAP treatment, which provided a solid foundation for CAP-based cutaneous/subcutaneous tumor therapy.