A high quality tapered monocapillary (TP) using a high-precision fiber optic tower is designed,and the beam size,the transmission efficiency and the gain factor of the TP are measured. The experimental results showed that the beam size of the tapered capillary is below 20 microns. At 8.04 keV,the transmission efficiency of the TP is 13.86%,and at 2.5 mm to the exit of the TP,the gain factor of the TP is 85. At the same time,shadow software developed for beam tracing is used to simulate the beam size,the transmission efficiency and the gain factor of the TP,the simulation results matched well with the experimental results. The beam size of X-ray beam focused by using the TP was smaller than that of X-ray beam focused by using an X-ray lens.