The phrase "main focus area" is correct and can be used in written English.
You can use it when you want to refer to an area that you are focused on and spending the most time and effort on. For example: "The main focus area of this project is to increase efficiency."
Design of highly efficient multifunctional reaction processes for energy production is one of the main focus areas of Chemical Engineering.
Sony is positioning digital imaging, game and mobile as the three main focus areas of its electronics business and plans to concentrate investment and technology development resources in these areas.
However, given the breadth of research areas covered within the main focus areas of the program, the opportunities for students to make significant contributions (and find jobs upon graduation) are legion.
Athletic performance, safety, and coaching are the three main focus areas in sports science at the moment; career entry points range from health sciences to exercise science and even engineering.
The main focus areas of this research are quality image restoration at higher noise densities of RVIN and achievement of lower computational cost of the proposed detection and filtering technique.
The package of school interventions covers five main focus areas: education; water, sanitation and hygiene; health; protection of vulnerable children; and community participation.
The young leaders worked together over the three-day meeting to produce their collective recommendations with regard to maternal, infant and child health, the main focus areas of the AU Summit.
Goals for 2012-2013 ThExecutiveve Director's report gave Executive Board members and delegates a wide-ranging overview of the results that UNICEF and its partners achieved in its main focus areas last year.
