This study was aimed to develop a simple, rapid, accurate and wound-free single-tube multiplex polymerase chain reaction (PCR) assay, which can be used for molecular screening and prenatal diagnosis of 3 types of the commonest deletional alpha-thalassemias in Chinese population. The deletional alpha-thalassemias free fetal DNA of 50 anemic pregnant plasma were detected by means of single-tube multiplex PCR with 4 groups of primers designed by using the gap-PCR protocol. The results showed that 5 cases were found to be alpha-thalassemias in free fetal DNA of 50 anaemia pregnant plasma, out of them 3 cases were the Southeast Asia type of deletional alpha-thalassemias, 2 cases were alpha-(3.7) type of deletional alpha-thalassemias (rightward deletion). It is concluded that the single-tube multiplex PCR assay presented in this study is a simple and convenient, rapid and accurate method for detecting 3 common deletional alpha-thalassemias, and use of this method has an important significance for the deletional alpha-thalassemias to ensure the population health quality and reduce the social burden.