This study aims had discussed the differences in both parental attitudes toward domestic sex education and sex knowledge of the sixth-grade students of elementary schools from different backgrounds, and the relation between their parents' attitudes toward domestic sex education and their sex knowledge.This study has been performed by collection of questionnaire and statistical analysis. The data collected from the investigation, is examined by independent sample t-test, one-way ANOVA, Pearson Product-Moment Correlation. This conclusion are as follows:1. Parental attitudes toward domestic sex education would be varied from different gender of children, and it would influenced parent-child communication and the atmosphere of family discipline.2. Children have a mid to high level of sex knowledge, and "the awareness of sexual harassment and sexual assault" is at the highest scores.3. Children' sex knowledge would be influenced by the educational attainment of parents, family type, parent-child communication, and the atmosphere of family discipline.4. If the consciousness of parental attitudes toward domestic sex education is more positive, their children's sex knowledge will be better.