Abstract: Using the Met Office large eddy model (LEM), a series of boundary-layer convection and deep convection experiments are performed to examine the characteristics of turbulence and deep convection triggering mechanism under different initial potential temperature and specific humidity conditions over wet and dry surfaces. Model results indicate that the mixed layer is warmer and drier over dry surface with a larger depth, and the opposite is true over wet surface. Because the surface sensible heat flux is more efficient in the formation of thermal turbulence, turbulent mixing and entrainment are stronger over dry surface, making the water vapor mixing ratio and equivalent potential temperature more uniform within the convective boundary layer (CBL) but a greater negative disturbance at the top of the CBL. The convection structure is the same as the bubble-like convection with a horizontal net-like structure over both wet and dry surfaces, but more vigorous over dry surface. The triggering of deep convection over different surfaces varies dramatically with the initial atmospheric condition. With weak atmospheric inversion (0.15 K/(100 m)) in the 1－3 km layer, deep convection first occurs over dry surface, but the accompanied clouds are thinner than those over wet surface because of the smaller convective available potential energy. Increasing the inversion intensity in the 1－3 km to 0.55 K/(100 m) not only delays the formation of clouds, but also decreases the cloud thickness. Only when combined with high initial specific humidity at the top of the CBL, can deep convections occur, also first over dry surface, and the associated clouds are thicker as a result of a significant cooling of the CBL top.