The purpose of this study was to investigate knowledge types which the elementary science gifted students would use when solving a science problem, and to examine characteristics and types that were shown in the science problem solving process. For this study, 39 fifth graders and 38 sixth graders from Institute of Education for the Gifted Science Class were sampled in one National University of Education. The results of this study were as follows. First, for science problem solving, the elementary science gifted students used procedural knowledge and declarative knowledge at the same time, and procedural knowledge was more frequently used than declarative knowledge. Second, as for the characteristics in the understanding step of solving science problems, students tend to exactly figure out questions' given conditions and what to seek. In planning and solving stage, most of them used 3~4 different problem solving methods and strategies for solving. In evaluating stage, they mostly re-examined problem solving process for once or twice. Also, they did not correct the answer and had high confidence in their answers. Third, good solvers had used more complete or partially applied procedural knowledge and proper declarative knowledge than poor solvers. In the problem solving process, good solvers had more accurate problem-understanding and successful problem solving strategies. From characteristics shown in the good solvers' problem solving process, it is confirmed that the education program for science gifted students needs both studying on process of acquiring declarative knowledge and studying procedural knowledge for interpreting new situation, solving problem and deducting. In addition, in problem-understanding stage, it is required to develop divided and gradual programs for interpreting and symbolizing the problem, and for increasing the understanding.