Abstract: To study the effect of height–diameter ratio on the uniaxial compression performance of gangue-cemented backfill columns, five groups of cylindrical specimens with height–diameter ratios of 0.5, 1.0, 2.0, 3.0, and 4.0 were prepared for uniaxial compression tests. At the same time, digital image correlation technology and acoustic emission were used for monitoring, and the stress curve, strain curve, apparent strain, acoustic emission ringing, energy, and impact number of the backfill column were recorded. The obtained data were processed and corresponded with each other with time to explore the failure characteristics of different height–diameter ratio backfill bodies. The results show that the peak stress and peak strain of gangue-cemented backfill decrease exponentially with increasing height–diameter ratio. The failure form of the backfill column changes from global failure to local failure when the height–diameter ratio is greater than 2.0, and a local strain of more than 16% can lead to the overall instability of the backfill column. When the height-to-diameter ratio of the backfill column increased from 1.0 to 4.0, the damage degree for the backfill column decreased to 11%. The proportion of damage of backfill bodies in the cumulative ringing count rapid rise region increased from 22.6% to 72.3% with increasing height–diameter ratio and reached 40.9% when the height–diameter ratio was greater than 2.0. The rising speed accelerated, and the concentration of damage was higher. The final cumulative ringing count of acoustic emission reached a maximum at a height–diameter ratio of 2.0, and the position of ringing concentration was greatly influenced by this ratio. The ratio of acoustic emission energy-to-ringing count (E/C) reacts to the intensity of energy release. The average E/C increases from 1.26 to 2.76 with increasing height–diameter ratio. Before the peak stress, the rising speed of E/C decreases above a height–diameter ratio of 2.0, and after the peak stress, the E/C rises faster above a height–diameter ratio of 2.0. Before the peak stress, the intensity of the failure of the backfill column reaches a maximum when the height–diameter ratio is 3.0, and after the peak stress, the failure process is more violent for the backfill column with a height–diameter ratio greater than 2.0. The test results provide a reference for selecting the height–diameter ratio of the backfill column in structural backfill mining.