The study identified 04 criteria to evaluate intentional attention status and 06 tests to assess the physical fitness of children with mild mental retardation of 6 - 9 years old in Mekong Delta Vietnam, at low and near - medium levels. Thereby, the study applied experimentally 16 physical activities belonging to 2 groups. Group 1 is physical fitness (including exercises on basic motor skills), Group 2 is the movement games exercise, which has applied the exercises into practice to improve the children's ability of intentional attention and physical fitness. Study on applying selected physical activities according to specific programs for children aged 6 - 9, mild mental retardation at some specialized schools in Mekong Delta for 10 months. The results show that: The intentional attention of children aged 6 - 9, mild mental retardation has a positive change, children have a significant improvement in the concentration of attention and Sustainability in attention attributes. Physical fitness, at all ages, has improved. However, when practicing according to the selected physical activities, the experimental group outperformed the control group in the following tests: Standing long jump (cm), One - leg standing balance (s), Throw a ball at a target (time), Forward bend sitting posture (cm) in 9 – year - old female, in other tests the experimental group improved better than the control group.