Abstract: Long-throated flume with an advantage of less head loss, higher precision of flow measurement and structures easy-to be built, has not been researched completely, and it is a new kind of flow measurement structure. But defects still exist in the theory associated with computation. Firstly, the effect of local head loss caused by end contractions was neglected. Secondly, the contraction coefficient of inlet section is not presented. Thirdly, the optimum shape of structures is not determined. Through a series of hydraulic experiment, the contraction coefficient is determined to be 1∶3. The ratio of sill-referenced head to the throat length for best performance is 0.07～0.7 which is suggested to be 0.6 for design. The formula to calculating head losses in the contraction section were revised. And the corresponding error decreases from 5% to 1.5%. The modular limit is up to 0.928. And a long-throat flume CAD software system was developed.