The aim of this research is to develop a test to determine the Science ability of 6th grade students. For this purpose, taking into consideration the 6th grade Science course outcomes; ability test was developed and validity and reliability studies were conducted. In the study, the steps of determining the purpose of the test, determining the properties to be measured, writing the items, reviewing the items, preparing the trial form, applying the trial form, scoring the test, item analysis and selection, and the final form of the test were followed, respectively. The study group of the research consists of 295 students studying in two different schools. According to the findings, item difficulty indexes of the questions in the developed ability test ranged between 0.26 and 0.80, while item discrimination indexes varied between 0.32 and 0.68. Item-total correlations of questions take values between 0.27 and 0.51. While the overall difficulty coefficient of the questions in the test was 0.53, the discrimination index was calculated as 0.47. The KR-20 reliability coefficient calculated for the reliability of the test was 0.84, and the split-half value was 0.71. It can be said that the ability test developed in line with all these results is valid and reliable.