The purpose of this study was to compare socio-linguistic characteristics and instructional influences of two different types of texts, which were narrative and expository. Socio-linguistic characteristics of two different types of texts were analyzed in their content specialization, linguistic formality, and social-pedagogic relationships. Expository texts showed strong scientific classification, and medium level of linguistic formality, and low level of social-pedagogic relationships. Narrative texts showed different characteristics. The instructional effects were investigated with 91 fifth grade elementary students in three classes. Each class was randomly assigned into three groups: expository text group, narrative text group, control group. The results showed that the science achievement scores of the narrative text group was higher than those of other groups. The affective domain test scores of the expository text group were higher than other groups. The perception of students on informational science text were generally positive both types of texts.