The production period is one of the main characteristics in the evaluation of economic activity level and enterprise recovery degree. Focused on the large deviation problem in the main production time extracting process, this paper proposes to adopt Dynamic Time Warping (DTW) to the measurement of main production period of power loads. After constructing a reference load curve, the DTW method is adopted to realize the optimal mapping of the test curve and the reference curve by the stretch out or draw back the two curves in time dimension. Then, the main production period of test load could be calculated by searching in the optimal warping path table. Finally, the effectiveness of the method is verified with experimental results of typical load curves from a southwest district. This paper also analyzes the influence of abnormal measurement data on the recognition of main production period. Meanwhile, the comparison results show that the main production period calculated with algorithm proposed in this paper is more accurate than the method of identifying the rising and falling points.