Background: Current development in stool- and cell-free DNA (cfDNA)-based technologies have demonstrated promising potentials in colorectal cancer (CRC) diagnosis. However, early detection of CRC and advanced adenoma (AA) remains challenging. Micronuclei (MN) are extranuclear bodies containing chromatin segments resulting from errors in DNA repair. Elevated levels of MN+ erythrocytes have been studied in genotoxicity testing and cancer diagnosis. We have developed a method (WO2021/228246 A1) for purifying and sequencing micronuclei DNA (mnDNA) in erythrocytes from peripheral blood. Here, we compared mnDNA between healthy donors (HDs) and CRC patients and explored its application for early cancer diagnosis. Methods: Peripheral blood (1ml) was obtained from a training cohort of 987 individuals, a validation cohort of 246, and an independent test cohort of 193. mnDNA was isolated and sequenced from erythrocytes. Genome-wide analysis identified distinctive mnDNA features between HD and CRC. Predictive models using these features were developed to differentiate CRC and AA from HDs. A clinical trial comparing mnDNA with an approved multitarget stool DNA test (sDNA-FIT) was also conducted on 60 individuals (42 HDs, 6 AAs, and 12 CRCs). Results: Genome-wide analysis of mnDNA revealed substantial differences in distribution patterns between HDs and CRC patients. The predictive model built on mnDNA features achieved an AUC of 92.98% (95%CI: 87.85-98.12%), with an 88.64% sensitivity and 92.75% specificity in the independent test cohort. The model identified early-stage (stage I-II) CRC and AA with sensitivities of 83.33% or 69.56%, respectively. Comparing mnDNA to sDNA-FIT showed superior overall sensitivity (83.33% vs. 61.11%), AA sensitivity (83.33% vs. 16.66%), with comparable specificity (85.71% vs. 88.10%). Conclusions: Our results demonstrate that mnDNA from a small amount of peripheral blood enable accurate detection of AA and early-stage CRC. As a type of cytoplasmic DNA, mnDNA can provide a valuable tool for early cancer detection, offering different underlying mechanisms compared to current methods. A larger clinical study (NCT05875584) is ongoing and will further validate the application of mnDNA in early cancer detection.