The miRNAs are non-coding small molecule RNA that regulate target mRNAs on the post-transcriptional level or affect their stability by binding to the 3′UTR region of target mRNAs, and thus participate in a variety of biological functions, such as development, differentiation, cell apoptosis, and metabolism. In recent years, a lot of studies found that the imbalance of miRNA levels can cause a variety of diseases, such as cardiovascular disease, cancer, and pulmonary hypertension (PH), etc. This paper reviews research progresses of the effects of miRNAs on the development of PH and being used as diagnostic biomarkers and therapeutic target of PH.