The present study aims to recommend the normal upper limit, the acceptable upper limit, the subclinical lead absorption and intoxication diagnostic criteria in an effort to re-evaluate the current national diagnostic criteria for the occupational chronic lead poisoning. The study was conducted on 330 lead exposed workers and 100 non-exposed controls based on the determination of blood and urinary lead, porphyrin metabolism indices, as well as other indices under a nationwide quality control program. The data were subsequently treated by the curve fitting, multi-step transformation to Gauss distribution,and discriminant analysis with the aid of a SAS software package. The relationships between the air lead and blood lead level with ceftain biological parameters indicative of excessive lead exposure and poisoning were well established. The sensitivity, specificity,accuracy, false positive and false negative results of these critical values were also fully evaluated. This study would be useful for the amendment of the new edition of the national diagnostic criteria for the occupational chronic lead poisoning in China and would providenew approaches for similar investigations The present study aims to recommend the normal upper limit, the acceptable upper limit, the subclinical lead absorption and intoxication diagnostic criteria in an effort to re-evaluate the current national diagnostic criteria for the occupational chronic lead poisoning. The study was conducted on 330 lead exposed workers and 100 non-exposed controls based on the determination of blood and urinary lead, porphyrin metabolism indices, as well as other indices under a nationwide quality control program. The data were succeeded by the curve fitting, multi-step transformation to Gauss distribution, and discriminant analysis with the aid of a SAS software package. The relationships between the air lead and blood lead level with ceftain biological parameters indicative of excessive lead exposure and poisoning were well established. The sensitivity, specificity, accuracy, false positive and false negative results of these critical values ​​were also fully evaluated. This study would be u seful for the amendment of the new edition of the national diagnostic criteria for the occupational chronic lead poisoning in China and would provide new approaches for similar investigations