Pile-plank structure is a new foundation under rail. It has been applied in China, because of its advantages that it can control the foundation settlement effectively and speed up the progress of construction. Zhengzhou-Xi'an high-speed rail is designed to a 350km/h high speed rail. To control the post-construction settlement, speed up construction schedule, this measure is applied in the deep collapsible loess foundation, the first time in the world. To guide the engineering design and to form a theoretical system, field test researches were conducted in appropriate working points, mainly including stress-strain test of bearing sheet and contact stress test between bearing sheet and foundation.