Abstract:We detail the far-field radiation patterns of low-frequency elastic waves generated by different axially symmetric sources in fluid filled borehole. Axially-symmet-ric sources are point volume source and point volume array source which are aligned along borehole axis, the radial stress source and radial stress array source which are distributed on borehole wall, and the tangential stress and tangential stress array sources which are on borehole wall. Source frequency ranges are discussed.and radiation patterns of P and S-waves generated by different kinds of sources are estimated numerically. The research result says that low-frequency far-field approximation is applicable to the downhole source which has frequency below 700Hz and is placed in a borehole 10cm in diameter. Both the point volume source on borehole axis and the radial stress source on borehole wall produce tube wave in borehole.but P and S-waves in formations. The tangential stress source on borehole wall only causes P and S-waves in formations. Array sources enhance radiation greatly.