The self-directing work of pupils in learning the subject. The principles of nature is the most existent in the application of pupils' experiments. It is necessary to determine the level of the pupils' self-reliance if order to advance and modernize teaching. Aim of this work is the analysis of the attitudes of pupils from the fourth grade primary school to the application of the experiments during the lessons of Principles of nature. In this work descriptive and analytical methods are used. We polled 105 pupils of the fourth grade. We concluded by using output data that pupils like to use experiments. They would like to have more experiments and to deduce by themselves. Most of them carry out experiments only during the lessons of The principles of nature. They have positive attitudes about methodology of presentation of experiments and their applications. They don't know how to write down experiments in their notebooks. They have positive and regular attitudes to experiments as the source of knowledge in learning Principles of nature.