Abstract: In order to made the physical dimension of nuggets meet the needs of mechanical properties, the inverse design of welded joint is introduced.Based on the mechanical properties, the qualified nugget sizes are determined.According to these, the numerical model is created.Through simulated calculation, the current parameters can be determined.Three kinds of regular shape nugget are used to research the relation between the mechanical properties and nugget sizes.Based on the stress graph, the diameter of nugget and the penetration rate varying with the tension stress, the nugget shapes are evaluated, the one which the stress distribution is the most evenly and the stress concentration is the most little is selected. According to the physical dimension of the nugget, the current parameter curve used for forming nugget is simulated by finite element simulate method.