In order to ensure that the Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) system can run accurately,it is necessary to measure the position of optical fibers on the focal plate of LAMOST. From the view of practical applications,the detection precision of light centroid method is introduced. Connected with a variety of experiments based on the theoretical analysis,the measuring conditions,such as the light spot size,the camera aperture and the light intensity on the end of fibers,were detailedly studied and their relationships to the precision of light centroid method were specifically analyzed. In addition,the centroid movement caused by change of light intensity was revealed. Finally,according to the result of experiments,the best detection conditions are provided for the factual measurement.