miRNAs are a new class of non-coding small RNAs that exist in many species. They play important roles in many physiological and pathophysiological processes by inhibiting the expression of target RNAs. Recent advances in miRNAs are beginning to be predicted and identified using several technological approaches, such as miRNA cloning, hybridization with various probes, and PCR-based detection. In the past few years, miRNA microarray technology has become the reference technique for monitoring the miRNA expression. In this review, miRNAs will be introduced and the characteristics of normalization methods in miRNA research will be discussed. The technical operations of miRNA profiling with microarrays will also be described, with an emphasis on probe design and labelling. The applications of the miRNA microarray in both basic and applied research will be summarized.