Objective:To investigate the expression of long non-coding RNA (lncRNA) CALCOCO1 in bladder cancer tissue and its effect on the proliferation and migration of bladder cancer cells by regulating miR-200a-3p.Methods:The relative expression levels of CALCOCO1 in bladder cancer tissues and adjacent tissues were analyzed by TCGA database. Human bladder cancer cells UM-UC-3 were selected, and the cells were divided into negative control group and CALCOCO1 group, and NC plasmid and CALCOCO1 plasmid were transfected into UM-UC-3 cells respectively. The expression level of CALCOCO1 in each group was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The proliferation and migration ability of UM-UC-3 cells were detected by MTT assay and Transwell migration assay. Bioinformatics technology was used to predict and dual-luciferase reporter gene experiments to verify the targeting relationship between CALCOCO1 and miR-200a-3p. The expression levels of miR-200a-3p in UM-UC-3 cells in each group were detected by qRT-PCR. Western blotting was used to detect the expression of UM-UC-3 cells proliferation and migration phenotype in each group. Measurement data were expressed as mean ± standard deviation ( ± s), t-test was used for comparison between two groups, and repeated measurement analysis of variance was used for comparison at different time. Results:Compared with adjacent tissues, the relative expression level of CALCOCO1 in bladder cancer tissues was significantly lower, the difference was statistically significant( P<0.01). The relative expression of CALCOCO1 in UM-UC-3 cells in CALCOCO1 group and negative control group was 9.66±2.51 and 1.07±0.59, respectively. The relative expression level of CALCOCO1 in CALCOCO1 group was significantly higher than that in negative control group, the difference was statistically significant ( P<0.01). Compared with the negative control group, the proliferation activity of UM-UC-3 cells in the CALCOCO1 group was decreased ( P<0.05), and the migration number of UM-UC-3 cells was significantly decreased ( P<0.01). CALCOCO1 had a binding site with miR-200a-3p ( P<0.01). The relative expression of miR-200a-3p in UM-UC-3 cells in CALCOCO1 group and negative control group was 1.02 ± 0.31 and 5.79 ± 1.68, respectively, the difference was statistically significant ( P<0.01). Compared with the negative control group, the expression levels of proliferation phenotype proteins CCNB1, CCNE1 and CCND2 in UM-UC-3 cells in CALCOCO1 group decreased, and the expression levels of migration phenotype proteins FOXC2 and Fibronectin decreased. Conclusion:The expression of CALCOCO1 is down-regulated in bladder cancer tissue, promoting the expression of CALCOCO1 can inhibit the proliferation and migration of bladder cancer UM-UC-3 cells through targeted down-regulation of miR-200a-3p expression.