Abstract: The racemization reaction rates of aspartic acid and isoleucine acid are determined in some animal fossils from strata where Peking Man and Dingcun Man where found. On the basis of the result from the determination, the accumulation ages and ancient environment of the strata are estimated. The accumulatin ages of the third and fourth strata at No. 1 Location of Zhoukoudian were about 200,000 years ago and that of the eleventh stratum about 687,000 years ago. The average temperature which Shandingdong has undergone since it began accumulation 8.3℃, which is under the present temperature. Based on the D/L values of amino acid racemization in a kind of shell fossil from some sections of Dingcun, Shanxi, it is estimated that the Living ages of Dingcun Man were about 700,000-900,000 years ago.

Key words: Aspartic acid; Leucine; Racemization