Abstract:A fire inventory, surface monitoring data and numerical models were used to analyze the biomass burning aerosol (BBA) emission in Indochina Peninsula and its effects on haze in Southwest China and pre-monsoon precipitation in South China. The BBA emissions in Indochina Peninsula mainly occur in March and April every year, and the peak emissions appear in late March to early April. Eastern Myanmar and Northern Laos are the major regions of the BBA emissions. The BBA in Indochina Peninsula mainly affects the haze in the southern cities of Yunnan, China at the surface. The emission from Myanmar is the most significant contributor to the pollution in these cities. The BBA in Indochina Peninsula could be transported over most parts of Southern China by the low-level southwest jet at the height from 800 hPa to 600 hPa. The transported BBA over Southern China could alter the spatial fraction of the pre-monsoon precipitation process by suppressing the convective precipitation and enhancing the non-convective precipitation, and making precipitation more concentrated near the shear line.