Abstract: Live-line work is a critical method for ensuring continuous power supply in electrical systems, and the performance of specialized insulating tools directly affects operational safety and efficiency. Traditional manufacturing of insulating tools relies on processes such as molding and injection molding, which suffer from long mold cycles, limited customization capabilities, and difficulties in forming complex structures. 3D printing technology offers a new pathway for customized tool development due to its advantages in rapid prototyping, high design flexibility, and elimination of the need for molds. This paper systematically reviews the technical foundations and material systems of 3D printing in insulating tool fabrication, analyzes the applicability of mainstream techniques such as FDM and SLA, and focuses on the electrical properties of 3D-printed insulating materials—including dielectric performance, breakdown strength, and volume resistivity. By examining engineering cases such as terminal isolation barriers in substations, the paper demonstrates the advantages of 3D printing in achieving precise customization that matches "operator–tool–work environment" requirements. Finite element simulations are used to analyze in detail how layered structures affect electric field distribution, quantifying the electric field enhancement factors under different printing orientations and the suppression effects of gradient layer thickness. The paper also discusses current technical challenges and explores future directions such as functionally graded materials and multi-material integrated printing. Research shows that 3D printing can significantly enhance the customization level and overall performance of insulating tools for live-line operations, gradually transitioning from prototyping to functional engineering applications.