Background:
This research is aim at obtaining information related to instrument development of Students' New Environmental Paradigm (NEP) based on their knowledge about ecosystem and Locus of Control (LOC)

Materials and methods:
A survey method has been carried out by selecting senior high school students randomly with n = 362 (first stage 2013) and n = 722 (2014). Data analysed by correlational analysis, alpha Cronbach and Factor analysis (CFA).

Results:
Research results reveal that there is no significant difference between two means of students NEP of 2013 and 2014 data. Internal consistency and high items validity found among items developed in 2013 and 2014. Reliability coefficient is also high (.905/2013 and .908/2014). Only knowledge about ecosystem has significant first order correlation with students NEP (.249/n = 722/ 2014). It is found also that there are three factors do not have “factor loading” equal to or more than .30, therefore, it should be omitted for next research. It is sound to be uni dimension with 12 factors (from 15 factors), based on 5 dimensions (62 becomes 46 items).

Conclusions:
It could be concluded that number of items and sample size affect instrument reliability and students NEP could be measures empirically.