The quality of meteorological observational data is res ponsible for t he results of meteorological and the related researches. How can we control the quality of meteorological data? It has been a scientific problem confronting met eorologists. The methods and technologies of data quality control (QC) are diffe rent in different countries. The cooperative researches in this field in the fiv e countries of northern Europe occupy a leading position in the world. The flows , methods and technologies for the real-time and non-real-time meteorological da ta quality control in Nordic countries are described. Their data quality control adopts a routine of four-level QC: QC0, QC1, QC2 and HQC. The methods include s ingle-station checking and spatial checking, and each kind of quality checking u ses different schemes. The QC flagging is very important in the process of data quality control. The flagging methods are different for different users. The sch emes of QC flagging are also dissimilar in the Nordic countries.