Abstract: Preliminarily experimental results indicated that the organisms causing citrus yellow shoot (CYS-BLOs), can’t be transmitted, by seed, but can be transmitted occasionally through xylem tissue.A low incidence of disease (3.3%) and a long latent period (15 months) was obtained when it was transmitted through xylem. Many pleomorphic bodies of bacterium-like organism, 90-640×100-1530 nm in size, with an envelope of 15-30nm in thickness, were observed in sieve tube cells of leafvein of the diseased plant caused by xylem transmission and it was absent in xylem vessels. It is possible that CYS-BLOs can transfer to sieve tube cells through xylem vessel in some case, and they grow well in sieve cells only.