Science career expectations can be affected by personal science beliefs and social supports. Framed in Expectancy-Value Models, this research studied the influence of science beliefs (science interest belief, self-efficacy belief and value belief) and social supports (parents and teachers) on students' science career expectations by the survey of 798 10th grade students. Based on Structural Equation Model, it was found that: 1) science interest belief, self-efficacy belief, value belief and parents' support can directly predict students' expectations of science careers; 2) the effect of student's perception from parents and teachers support on science choice preferences and career engagement are mediated through the effects on students' interest, self-efficacy and value in science. Therefore, teachers and parents should enhance students' science beliefs and identity for the improvement of their science career expectations.