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In order to improve the quality of hollow Cu tubes, a horizontal continuous casting technology was developed in a pilot scale by using electromagnetic field of commercial frequency, and the effect of electromagnetic field on structure and mechanical properties were studied. The results show that the structure of hollow Cu tubes is refined substantially with the application of electromagnetic field and the average grain grand is increased from 3.1 to 8.3 and the uniformity along the circumference of the structure is improved obviously at the same time. The tensile strength is increased by 40% and the elongation is improved by 50% averagely if compared to those without electromagnetic field.