Robotized endoscope holder in laparoscopic surgeries allows surgeons to control the endoscope without the assistants' intervention. In this paper, a new method is proposed for the automatic 3D-tracking of laparoscopic instruments in real-time to provide more convenient interactions between surgeons and the robotized endoscope holder. The method is based on the 3D position measurements of the insertion points of the instruments and the strip markers, combined with the depth estimation of the instruments. The results of our experiments show that our method is fast and robust in the simulated laparoscopic surgeries.