This research have purposed improve the ability of understanding concept of Natural Science at student and also to know the student activity and the teacher in studying Natural Science studies about object and the character by applied Inquiri learning model. This research is class action abservation. This research be held on two cycles each cycle consisting of two meetings. Each cycle learning which consists of 4 phases, starting from planning, action, observation, and reflection. The research subjects fifth-grade students in Pohjejer I/454 State Elementary School Mojokerto totaling 14 students. Research data obtained from observation, testing and polling. Sheets of observation to observe teacher activities and students during the learning process. Observation data are analyzed in from of percentage. Test used to asses students Science learning after by applying the inkury learning model. Polling used to know the student response after study Science by applying the inkuiry learning model. The result of this research is showed that by using application of inquiry learning model the ability of understanding concept of students increase. this matter is visible from complete percentage on the first finding is 21,4%, cycle I is 64,3% increase 42,9% from first finding. Cycle II is 92,8% increase 28,5% from cycle I. From this result we can conclude that using the application of Inquiry learning model can improve the ability of understanding concept of Natural Science at students of the fifth grade students of Pohjejer I / 454 State Elementary School Mojokerto. Based on this observation result so teachers are suggested to try applying inquiry learning model in Science studies to incease students concept matering.