We have developed a weapon effectiveness evaluation model for top-attack smart munitions(WEEM/TASM), which is a many on many Monte Carlo Model evaluating the effectiveness of top-attack smart munitions against armoured ground vehicles. In this model the battle is reduced to a one-sided battle situation in that the target vehicles are regarded as being stationary and passive. It can simulate the whole attack process of smart munitions from firing artillery dispenser to sensing and hitting processes after dispense. It can also calculate the probability of kill of each target and the numbers of rounds required to fulfill the degree of damage in statistical manners. In this paper, we describe the basis for our design concepts reflected in the model to simulate the weapon effectiveness of top-attack smart munitions and provide simulation results for an example case.