The phase-match and amplitude characteristics of high harmonics generation in gas filled micro-capillary have been analyzed. The results show that the order of harmonic can be selected by adjusting the gas pressure, the laser intensity and the inner diameter of capillary. The adjustment is depended on the dispersion properties of gas media . The amplitude of harmonics generated in gas filled capillary is two orders higher than that of gas jet, and the spectrum is become more monochromatic when the radius of the capillary is smaller. A high brightness tunable coherent soft X-ray source can be produced through interaction of fs intense laser with gas filled microcapillary.