The invention relates to the technical field of biology, in particular to a method for extracting mciro-RNA from plasma and a kit thereof. The method comprises the steps that a lysate is added into a plasma sample, and a protein removal solution is added; an RNA extraction reagent is added for performing RNA extraction, then, chloroform is added for oscillation mixing, and centrifuging is performed to collect supernatant liquid; a precipitating agent and a settling agent are added, and centrifuging is performed to collect sediments; a washing solution is used for performing washing, centrifuging is performed to collect sediments, RNase-free water is used for performing dissolution. According to the extraction method, firstly, sample cracking and protein removal are performed, and then RNA extraction is performed, so that proteins combined with the micro-RNA are modified to release the micro-RNA, and the integrity of the micro-RNA is kept. According to the kit, the lysate and the protein removal solution are used at the same time for helping sufficient degradation of proteins combined with the micro-RNA, and the precipitant isopropanol and the settling agent glycogen are used at the same time, so that the micro-RNA recycling efficiency is greatly improved.