Abstract: The basic concepts and equations of Smoothed Particle Hydrodynamics(SPH) are reformulated.The strategy and practice of programming a 3-dimensional SPH code and also the check of the code are outlined.The influences of artificial viscocity together with artificial heat flow are investigated numerically.As an example of the application,the results of numerical simulation of a 3-dimensional hypervelocity impact problem are given with some existing problems of SPH method.