A numerical simulation study was conducted on the co-optimization of injector configuration parameters and injection strategies for diesel-piloted high-pressure direct injection ammonia combustion. Results indicate that reducing injector offset increases the proportion of effectively-ignited ammonia spray，improving combustion efficiency and thermal efficiency. Under high load conditions，the ammonia-first-diesel-later(AD) injection strategy leads to obstruction of the diesel flame by the ammonia spray，preventing full effective ignition of ammonia，with maximum combustion losses reaching 27.62%. Using a two-stage ammonia(ammonia-diesel-ammonia，ADA) injection strategy or optimizing the side injector nozzle insert distance effectively avoids interference between the ammonia spray and diesel flame distribution，enhancing the ignition and combustion processes. The optimal solution features：side nozzle offset of 10 mm，insert distance of 6 mm，diesel-first-ammonia-later(DA) injection strategy at low load(thermal efficiency：49.68%)，and AD injection strategy at high load(thermal efficiency： 50.75%). The sub-optimal solution uses a side nozzle offset of 10 mm with other parameters unchanged：DA injection strategy at low load(thermal efficiency：50.26%) and ADA injection strategy at high load(thermal efficiency： 49.93%).