Abstract: To address the issues of uneven fuel spatial distribution and low air utilization in side-mounted fuel injection systems on opposed-piston two-stroke（OP2S） diesel engines, the influence of the double-swirl inner chamber configuration parameters on combustion heat release was investigated using CONVERGE software. The results show that the chamber configuration significantly affects the momentum distribution and velocity field of the fuel jet after wall impingement, thereby altering the fuel spatial distribution and mixture quality. The differences in combustion are primarily reflected in the afterburning stage. With a smaller inner chamber inclination angle （27.8°）, the velocity field covers a smaller area, and the fuel rotates within the inner chamber pit. With a larger inclination angle （50.0°）, significant momentum loss occurs, and the fuel jet tends to move toward the outer chamber. An appropriate inclination angle （32.5°） can induce a high-speed and widely distributed velocity field, which transports the fuel to the root of the inner chamber, improves air utilization, and reduces locally over-rich mixtures. As the inner chamber inclination angle increased from 27.8° to 32.5°, the mass proportion of fuel within the suitable range for combustion increased from 33.5% to 34.6%, the combustion duration shortened from 28.84° to 24.67°, and the indicated thermal efficiency improved from 49.55% to 51.84%. However, further increasing the angle to 50.0° led to a decline in combustion and power output performance.