This study aimed at exploring the effectiveness of teaching with Desmos program in acquisition concepts of functions at grade ten and student's motivation in learning mathematics. To verify that, a teacher's guide was prepared for teaching functions using that program. The researcher has also prepared a test about the function's concepts and its validity and reliability were verified and checked. The sample of the study consisted of (58) grade 10 students from a basic education school in Muscat Governorate. They were divided into two groups: an experimental group who studied the unit of functions by using Desmos program and a group who studied the same unit using the usual teaching method. The study found that: There is a statically significant difference at the level of significance (a s 0.05) between the mean score of the experimental group and the mean score of the control group in the test for the favour of the experimental group. students There is a statically significant difference at the level of significance (a s 0.05) in the test to measure the motivation due to learning mathematics for the favour of the experimental group. Considering these results, the researcher recommended the necessity of applying and using Desmos program in teaching algebra different topics, based on the positive effects the study had shown in gaining the concepts of functions with students.