While there is increasingly strategic importance in knowledge, it is facing new challenges to manage knowledge effectively. The paper studies the motivational construct model for knowledge sharing from the perspective of content theories and social motivation theories. The data collected by using the questionnaire survey from a variety of industries was analyzed on the basis of interviews and pretest. The results of exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) showed the motivational construct model for knowledge sharing was comprised of existence motivation, relatedness motivation, growth motivation and norm motivation. The results extended the perspectives for knowledge sharing motivation and provided theoretical evidences for facilitating knowledge sharing behavior.