MicroRNAs (miRNAs), a category of small molecules that possess significant regulatory capabilities, have been extensively employed as biomarkers in the domain of biosensing to facilitate the early detection of diverse ailments. However, sensitive and accurate miRNA detection remains a huge challenge due to the high similarity between the homologous sequences and low abundance. Therefore, it is essential to develop methods with high sensitivity and specificity for miRNA detection. In this study, we present the development of a signal cycle-based platform that utilizes cyclic reverse transcription (CRT) and CRISPR-Cas12a to enable the precise and sensitive detection of microRNAs. The CRT mechanism facilitates precise target recognition in the presence of target miRNA, thereby converting miRNA signals to DNA signals. The trans-cleavage activity of the Cas12a protein is triggered by the formation of complete hairpin-shaped CRT products; this results in the cleavage of the DNA section contained in the H probe, while the RNA section ("4"@MBs) remains loaded onto the surface of magnetic beads (MB). By binding with the "reporter" sensor, the "4" sequences create an RNA/DNA duplex that the duplex-specific nuclease (DSN) can recognize. The "reporter" probe is thus metabolized, leading to the reappearance of the fluorescence signal. By capitalizing on the exceptional fidelity and selectivity of CRISPR/Cas12a, as well as the substantial impact of triggered enzymatic cycle amplification, this approach demonstrated remarkable sensitivity and specificity in miRNA detection, even in a complex environment containing 10% fetal bovine serum (FBS) and a serum sample. In contrast, a detection limit of 3.2 fM is conceivable. Furthermore, this approach maintained a notable degree of stability, which was anticipated to result in the detection of miRNAs in an effective and sensitive manner.