Using four cumulus convection parameterization schemes and the nonhydrostatic mesoscale numerical model MM5,the torrential rain on 25—26th July 2003 in Yunnan is simulated.The analyses on the precipitation distribution,precipitation intensity,and meso-scale low flow characteristics of the rain storm simulated indicate that the ranges of heavy rain(>25mm) simulated by Grell,Kain-Fritsch,and Betts-Miller scheme are all smaller than the observed;the precipitation intensity simulated by Betts-Miller scheme is much greater than the observed;and simulated results by Anthes-Kuo scheme are relatively close to the observed.The Anthes-Kuo scheme not only simulates well the process,range,intensity and central position of the heavy rain,but also reproduces well the some meso-scale characteristics of the low pressure circulation system.