【Objective】Forage　maize　is　a　crop　cultivated　in　the　Yinda　Irrigation　District　in　Gansu　province,　China.　This　paper　investigates　the　influence　of　planting　density　on　its　growth,　yield　and　quality.【Method】　The　variety　of　Long　Silage　No.1　was　used　as　the　model　plant.　The　field　experiments　compared　five　planting　densities:　5.6×104　plants/hm2　(M1),　6.8×104　plants/hm2　(M2),　8.0×104　plants/hm2　(M3),　9.2×104　plants/hm2　(M4),　and　10.4×104　plants/hm2　(M5).　In　each　treatment,　we　measured　plant　traits,　yield　and　quality　of　the　plant　at　its　maturity　stage.　【Result】①　Plant　height　and　stem　thickness　both　varied　with　planting　density　parabolically.　With　the　increase　in　planting　density,　cob　length,　cob　thickness,　fresh　cob　weight,　the　number　of　rows　of　grains　and　the　number　of　rows　in　cobs　all　increased　first　and　then　decreased　when　planting　density　exceeded　8.0×104　plants/hm2.　②　With　the　increase　in　planting　density,　fresh　grass,　hay　and　kernel　yields　increased　to　182　146.72　kg/hm2,　91　054.35　kg/hm2,　and　24　278.68　kg/hm2,　respectively,　when　planting　density　was　8.0×104　plants/hm2,　and　then　decreased　after　planting　density　exceeded　8.0×104　plants/hm2.　③　Compared　with　M4　and　M5,　M3　increased　the　crude　protein　by　8.31%　and　12.49%,　the　crude　starch　by　10.58%　and　15.71%,　and　the　fat　contents　by　10.38　and　19.71%,　respectively.　It　was　found　that　the　neutral　washing　fiber　was　the　highest　in　M5　and　the　least　in　M3.　Compared　to　M3,　M5　increased　the　neutral　detergent　fiber　by　7.78%.【Conclusion】　A　planting　density　of　8.0×104　plants/hm2　is　optimal　for　yield　and　quality　of　forage　maize　cultivated　in　the　Yinda　Irrigation　District.　©　2024　Office　of　Journal　of　Irrigation　and　Drainage,　Farmland　Irrigation　Research　Institute,　Chinese　Academy　of　Agricultural　Sciences.　All　rights　reserved.