In the TRAMS_RUC_1 km (Tropical Region Assimilation Model for South China Sea_The Rapid Update Cycle_1 km), the initial field and lateral boundary condition scheme, including its vertical resolution, time update frequency, and completeness, were revised and tested with a typical squall line case. Preliminary analysis revealed the following aspects: (1) The mesoscale character of precipitation in the squall line was better simulated after increasing the vertical resolutions of the initial field and lateral boundary, with the increase in the vertical resolutions of the middle and low layers playing the most critical role. (2) The diurnal change of lateral boundary forcing became more accurate after increasing its time update frequency. The squall line moved south after using the high update frequency of the lateral boundary condition because of the strengthened convergence of moist flux along the coastline. (3) With the high vertical resolution and high update frequency of the lateral boundary condition, lateral forcing of the vertical speed and cloud particle had no obvious effect on the forecasting of the squall line. In general, the vertical resolutions of the initial field and lateral boundary needed to be increased. The time update frequency also needed to be increased. Meanwhile, the lateral forcing of the vertical speed and cloud particle could be omitted. The effect of the new scheme was verified against observations in April 2019 (which lasted for a month). The distribution pattern and diurnal cycle of the mean hourly precipitation were significantly improved with the revised initial field and lateral boundary condition scheme.