This Study aimed at exploring the effect of Guided–Inquiry based laboratory method and the Demonstration method on the achievement of scientific chemical concepts of female secondary students in Jordan. The study sample consisted of (n = 52), distributed into the Guided – Inquiry based laboratory group and the Demonstration group. An achievement test was constructed to assess the achievement in scientific chemical concepts of female secondary students; the validity and the reliability of the tool were tested. The results of the study showed that: There were statistically significant differences in achievement in scientific chemical concepts for female secondary students between the means of the two groups in favor of the Guided – Inquiry based Laboratory group. In light of this result, the study recommended implementing the Guided –Inquiry based Laboratory method to be used in science laboratory, scientific thinking. Pre and in- service science teachers training courses should be conducted on the Guided – Inquiry based Laboratory method to facilitate the using of such method in science teaching. It also recommended further research and studies on the effect of using such strategies on other learning outcomes.