lncRNA UCA1 was upregulated in ML cell lines.Knockdown of lncRNA UCA1 inhibited cell viability, migration, invasion,and prompted apoptosis of ML cells in vitro. LncRNA UCA1 could bind with miR-126 and downregulate miR-126 expression. Simultaneously, the anti-growth and anti-metastasis actions of lncRNA UCA1 knockdown on ML cells were reversed by miR-126 suppression. RAC1 was a target gene of miR-126,and the anti-ML actions of miR-126 were abolished by RAC1 overexpression.Moreover, PI3K/AKT and JAK/STAT signaling pathways were blocked by miR-126 overexpression while were activated by RAC1 overexpression.