Based on the focus pre-search a method is presented to measure the characteristics of the traverse focus error detection system:focus offset,focus error sensitivity and linear range.A periodical input voltage to focus actuator makes the traverse to do pre-search and the focus error signal is generated.Then from the focus error signal the traverse focus offset is calculated by the focus error occurring time,and the traverse focus error sensitivity and linear range are calculated by the focus error slope and peak-to-peak value.A traverse focus error detection system is measured.The method uses electric signal to measure the characteristics of the traverse focus error detection system,and doesnot need the close loop control and the three dimensional platform,and is easy to realize.