The invention provides a data sampling method and a merging unit for data sampling. The method comprises steps that firstly, two paths of data is verified, after verification passes, the two paths of data is respectively transmitted in positive and negative code formats; the positive and negative code data is respectively analyzed, if the data is valid, the data is stored in a data buffer area; resampling is carried out through two independent logic channels, and the data after resampling is stored to the data buffer area; the data of the data buffer area is sent to a CPU, the data is then verified and analyzed by the CPU, cross verification of the positive and negative code data is carried out, after all verification passes, the data is sent to a protection device. The method is advantaged in that hardware cost of the double configuration merging unit employed for guaranteeing data transmission reliability is reduced, double logic channel transmission of the sampling data is realized, and sampling reliability of the merging unit in high temperature and strong electromagnetic interference severe environments is further improved.