Abstract: In order to acquire the shortest straight pipe length and investigate the performance of cone flowmeter with installed upstream elbow, this study has put forward three different structure prototypes with lOOmm diameters and the p values being 0.45. 0.65. 0.85 respectively. Simulation and experiment investigations have been carried out with the installment of a upstream single 90o elbow, double closed 90o elbows of "S" shape under the same plane and double closed 90oelbows under the vertical plane, with the medium of normal temperature water and Reynolds numbers being 0.498 × 10~5 ~4.98 × 10~5 and 0.14 × 10~5 ~4.5 × 10~5 respectively. The numerical simulation result is consistent with the experimental conclusion. Through both of them, we ob-tain the length of the straight pipe for the cone flowmeter while the effects of the relative error and additive uncertainty of the averaged discharge coefficient on the installation of upstream el-bow have been considered.