Based on the on-sea measurements on net position and net mouth height (vertical opening) of the 400 m×143.44 m (headline 61 m) of Antarctic krill trawl used by the "Mingkai" krill trawler operated at South Shetland Island from February to July 2015, this paper analyzed the effects of towing speed and warp length on the net position and net mouth height. The net position and net mouth height were measured by DR-1050 depth instruments and the corresponding towing speed and warp length during trawling were also recorded. In this study, the net mouth height is defined as the difference in water depth between the headline and footrope, while the net position is defined as the water depth of the central position of the net mouth. According to the usual operation practice of the fishing vessel and characteristics of the krill aggregation, the range of warp length increased from 138 m to 258 m, with 20-m intervals, and tow speed increased from 1 kn to 3 kn with 0.5-kn intervals. The main results are as follow:(1) The net mouth height of the krill trawl studied ranged from 13.6 m to 24.1 m, while the net position ranged from 50 m to 70 m deep. (2) During trawling, net position was controlled mainly by the length of warp. For each additional 20 m from 138 m of the warp length, the net position decreased by 1.9 m on average, and the net mouth height reduced by approximately 1.1 m on average. Warp length showed significant effects on both the net position and net mouth height (<0.01). (3) When towing speed increased from 1.0 kn to 3.0 kn, average rise rate of the net position reached 2.9 m/kn with the variation of warp length changing from 138 m to 258 m. When towing speed increased from 1.0 kn to 3.0 kn, the vertical opening of net mouth average reduction rate reached 2 m/kn, accounting for 19.8% on average. Towing speed had a significant impact on the net position and net mouth opening (<0.05). (4) Analysis of the relationship between rate of net position change and towing speed expression showed that average rate of the net position change decreased first and then increased with different ranges of towing speed under different warp lengths. This result can not only provide useful reference for the Antarctic krill fishing vessel captain who can, according to the size or water layer of the krill aggregation and its relation with the location of the net, timely adjust the warp length and towing speed and control the net at the water depth for accurate fishing, but also provide basic information for Antarctic krill trawl model experiments and independent design of the Antarctic krill trawl net.