As an important measuring technique,the white light scanning interferometry can realize non-contact,fast and high-accuracy measurement.However,when measuring the large step structure,the white light scanning interferometry has the problems of long time measurement and low signal utilization.In this paper,a kind of speed-variable scanning technique is presented to measure the large step structure to expand its efficiency.This technique has two realizations:the pre-configuration mode and the auto-focusing mode.During the scanning process,the image collection is limited within the coherence area,and in other positions,the motion is speeded up.The speed-variable scanning is driven by the nano-measuring machine(NMM) which reaches nanometer precision and is controlled by the measurement software.The testing result of 100 μm step height illustrates that the speed-variable scanning can improve the efficiency compared with conventional fixed-step scanning and it keeps the same high accuracy.