This research has developed learning tools of inquiry models combined with advance organizers in order to activate students' initial knowledge and improve their problem-solving skills. This article focuses on delivering the trial phase of the development process. The trial phase used non-equivalent pre-test post-test control group design to determine the effectiveness the combination of inquiry learning models and advance organizer approach. The population involved high school students in Mataram city and sampling was done by using cluster random sampling technique. Two groups were chosen and divided into experimental and control classes. The instrument used in the study is problem solving essay test consisting of 5 questions. Data were analysed using the Mann-Whitney test at a 5% level of significance, followed by the effect size and N-gain to find out the level of students' problem-solving skills improvement. Based on the result, it was found that the students in the experimental class who used a combination of inquiry learning models and advance organizer had significantly problem-solving skills' improvement than the control class that only used inquiry learning models. Also. the experimental group had a higher ability to focus on the problems, make a plan and implement it to find the solutions.