Phosphodiesterase 4 inhibitors without vomiting of the present invention are compounds or prodrugs or solvates represented by formula (I) wherein R1 is an independent methoxy, bromine and substituted aryl; X is an optionally substituted six-membered heterocyclic ring; Y is —(CH2)n—, —NH(CH2)n—, and —NH(CH2)n—O—, wherein n is any value among 0, 1, 2 and 3; Z is an optionally substituted aromatic ring or an optionally substituted heteroaromatic ring. Phosphodiesterase 4 inhibitor without vomiting of the present invention are novel biphenyl series PDE4D inhibitors, and can be applied to treat depression and Alzheimer's disease, improve cognitive ability and avoid vomiting.