In order to enhance the speed of querying, tuples in databases should be indexed. According to the characteristic of data in rough relational databases, one approach to index uncertain data was put forward. Firstly, tuples of rough relational databases were represented by binary string; Secondly, based on Hamming distance which is used to describe the distance between two codes, the one between tuples was calculated and a distance matrix was constructed; Thirdly, On the basis of the distance matrix, tuples were classified and indexing of tuples was implemented. Finally, an algorithm for indexing of rough relational databases was proposed and illustrated by using a soil analysis example. The real world example shows that the proposed approach is useful and feasible.