Abstract: The growth response of silage maize and forage sorghum intercropping to the row ratio configuration was clarified, and the driving mechanism of productivity improvement in the intercropping system was discussed. An optimal intercropping mode for silage maize and forage sorghum in northwestern irrigated areas was proposed. The experiment was conducted from 2022 to 2023 at the pasture base of the Ningxia University Agronomy Land Reclamation Maosheng Company. With the aim of changing the row ratio with the same bandwidth, five intercropping row ratios of silage maize and forage sorghum 10∶2, 8∶4, 6∶6, 4∶8, 2∶10 (10M2S, 8M4S, 6M6S, 4M8S, 2M10S), and silage maize monoculture (SM), forage sorghum monoculture (SS), were established. The plant growth dynamics, dry matter accumulation, and land-use efficiency were analyzed. The results showed that 10M2S, 8M4S, and 6M6S all increased the dry matter accumulation of silage maize during the filling and harvesting periods, with increases of 6.46%–28.18% and 8.37%–13.81%, respectively, compared to monoculture silage maize. The effect of intercropping on the dry matter accumulation of 6M6S was relatively small after 60 and 80 days of sowing for forage sorghum. After 100 days of sowing, the dry matter accumulation of 6M6S increased. After 120 days of sowing (harvest period), the dry matter accumulation of 6M6S, 4M8S, and 8M4S increased. Among them, the dry matter accumulation of 6M6S after 100 and 120 days of sowing increased by 16.53% and 33.16%, respectively, compared to single cropping for forage sorghum. Simultaneously, the land equivalent ratio (LER) under each treatment was >1, with an average of 1.08–1.38 over 2 years. The land productivity increased by 8%–38%, indicating a significant intercropping advantage. Intercropping significantly increased forage yield and crude protein yield, with an average 2-year increase of 13.20%–41.93% and 22.43%–53.33% compared to silage maize monoculture, and 6.73%–33.82% and 0.34%–20.64%, respectively, compared to forage sorghum monoculture (except 2M10S), with the highest yield increase observed at 6M6S. The compensation effect of the five intercropping modes is greater than the selection effect, and the yield increase is mainly driven by the positive compensation effect. The LER is significantly positively correlated with compensation effect, and the yield increase rate of silage maize is significantly positively correlated with compensation effect. Overall, the 6M6S intercropping model has significant yield advantages and can be used as a suitable intercropping model in northwestern irrigation areas.