The research aim to teaching the biology subject with numbered heads strategy and it's effect in development of scientific thinking at fifth preparatory grade students. The research sample was restricted on fifth grade students of the bio science in zainab preparatory school for girls, where the sample was formed from (66) student they were distributed to two equal groups one is experimental was studied according to numbered heads strategy while the control group was studied by the usual way , and to measure the students ability on scientific thinking the researcher adopts ascale (taha,2016) consisting of (30) paragraphs for each paragraph (4) alternatives after applying the research tool pre and post on the two groups, the results showed a statistically significant difference in scientific thinking average scale. For the pre and post- test among students of the experimental group and in favor of post-test, the results also showed a statistically significant difference in development of scientific thinking between the two groups and in favor of experimental group.