A new 10-hydroxyl anthrone glycoside, 1, 8, 10 - trihydroxyl-1ObDglucopyrano- syl-3-methyl-10- C (S) b D- glucopyranosyl-anthrone-9 1 was isolated from the stem of Cassia siamea Lam. The structure was elucidated by spectral evidences, especially by 2 D techniques. A new 10-hydroxyl anthrone glycoside, 1, 8, 10 - trihydroxyl-1ObDglucopyrano- syl-3-methyl- 10-C (S) b D- glucopyranosyl-anthrone-9 1 was isolated from the stem of Cassia siamea Lam. structure was elucidated by spectral evidences, especially by 2 D techniques.