In this research study, ostracodes were examined that were originally collected by Tony-Dzuy et al. in 1991 and 1993 from the Second Member of the Khao Loc Formation at the Tong Vai section of Tong Vai Valley, North Vietnam. Two genera and five species are preliminarily recognized as follows: Sinoleperditia (Sinoleperditia) cf. yulinensis Wang, 1994, S. (S. ) subbrevis Wang, 1994, S. (S. ) liujingensis Wang, 1996, S. (S. ) tongvaien- sis sp. nov. and Qujingsia sp. They are assigned to the Sinoleperdiriinae Wang, 1994 except for the last one, which is a taxa of Beyr/chiidae M'Coy, 1846. In these four sinoleperditiine species, seven individual specimens possess bothtrailing chevron and adductor muscle scars; their ratios of vertical height of trailing chevron muscle scar (th) to that of adductor muscle scar (ah) range from about 0. 675 to 0.71, with a mean value of about 0. 694. The Sinoleperditi- inae bearing beds in tile Second Member of Khao Loc Formation may be approximately correlated with tile lower- middle part of Xitun Formation in Qujing of Yunnan or the Lower part of I.ianhuashan Formation of Liujing in Guan- gxi and are considered to be middle to late I.oehkovian, particularly late Loehkovian in age. The Sinoleperditiinae- bearing beds in the Second Member of Khao Loc Formation might be deposited in an intertidal environment.