Abstract: The effects of medium concentration on callus growth and the accumulation of chlorogenic acid and flavonoids of Eucommia ulmoides were investigated. The treatments were designed in B₅ medium supplemented with 0.5 mg/L NAA + 0.5 mg/L BA.The results showed that the callus growth was increased when KNO₃ content was increased,whereas chlorogenic acid and flavonoids contents were highest when KNO₃ concentration was 2/3 of original amount in B₅ medium.The 4/3 content of (NH₄)₂SO₄ in B₅ medium were best for the callus growth and flavonoids content and yield, whereas chlorogenic acid content was highest when (NH₄)₂SO₄ content was 1/3 of original amount in B₅ medium.The callus growth was highest when MgSO₄ concentration was 2/3,whereas chlorogenic acid and flavonoids contents were highest when MgSO₄ content was 1/3 in B₅ medium. The original content of NaH₂PO₄,CaCl₂ and MnSO₄ in B₅ medium were best for the callus growth and the accumulation of chlorogenic acid and flavonoids. The contents of ZnSO₄ and FeSO₄ in B₅ medium was best for the callus growth but chlorogenic acid and flavonoids contents was highest when ZnSO₄ and FeSO₄ concentration was 1/3 in B₅ medium.