MYH8 is an actin-based motor protin involved in integrin-mediated cell adhesion and migration. Heretofore, the association of MYH8 mutation and cancer is unclear. In this study, we investigated the biologic significance of novel MYH8 tail truncation mutation, R1292X, in acute myeloid leukemia (AML) which was discovered by whole-exome sequencing and targeted re-sequencing of 209 AML patients. The patients harboring the mutation all relapsed within 3.8–20.9 months. To explore the functional consequence of the mutation in AML progress, we established knock-in cell lines using CRISPR-Cas9 genome editing. Using the established mutant model, we assessed traits of cancer progress. The mutant cells had improved motility, which was confirmed by immunofluorescence staining, wound healing, transwell migration and adhesion assay. The cell morphology and cell cycle were altered to be accessible to migration and epithelial-to-mesenchymal transition (EMT) transcription factors were also increased. The Raf and p44/42 MAPK pathway was a major regulator of these characteristics proved by a screening of signal transduction and inhibitor assay. Further, a public cancer genome database (cBioPortal) shows that MYH8 tail truncation mutations occurring near the R1292 position of the genome may have a significant function in cancer. In conclusion, truncation of MYH8 could be a novel prognostic marker related to poor prognosis by inducing cell migration and EMT features, and inhibition of the Raf/MAPK pathway would be a therapeutic strategy for AML patients with MYH8 tail truncation.