Objective To evaluate the diagnostic value of 18F-FDG PET-CT in looking for tumor primary lesion with multiple bone metastasis.Methods 84 patients with suspected bone metastases were detected by routine imaging (X -ray,CT,MRI)in our hospital from May 2012 to September 2014 were selected,18F -FDG PET/CT were used to find the primary lesion.The final diagnosis were confirmed by tissue pathology or by clinical imaging follow -up.The diagnostic sensitivity,specificity and accuracy on tumor bone metastasis of 18F -FDG PET/CT were recorded.Results In 84 patients,primary tumor was found in 49 cases,of which 46 cases (54.8%)confirmed pri-mary tumor by operation or pathology,the other 3 cases were false positive;35 patients were diagnosed as non meta-static bone tumor by PET/CT,in which 34 cases were finally confirmed as non metastatic bone tumor by pathology and follow -up;accuracy,sensitivity,specificity of 18F -FDG PET/CT were 54.8%(46 /84),93.9% (46 /49)and 95.2%(80 /84);18 cases of lung cancer,9 cases of prostate cancer,7 cases of breast cancer,5 cases of lymphoma, 4 cases of renal cell carcinoma,2 cases of liver cancer,1 cases of Uterine sarcoma were included in 46 primary tumors.Conclusion 18F -FDG PET/CT has a higher specificity,accuracy as well as higher detection rate in search of multiple bone metastases,thus it is beneficial to the clinical therapy.