In traditional pulverized coal tangential firing boiler design, the uniform air distributing burner is always adopted to burn bituminite with fine ignitability, so that good furnace flame coefficient of fullness and high coal powder burn-off rate can be obtained. But such assemblage also brings too concentrated heat release rate in burners' zone which leads to slagging while burning clinkering coal, the local high temperature zone and uniform air distribution also lead to high NOx emission. In today's China, there are lots of tangential burning boilers without overfire air to decrease NOx emission, to add OFA on the top of burner group is a difficult and expensive work which may also brings other problems. In this paper, an idea that the upper primary air is moved to lower location to provide room for OFA is developed, using the concentrated primary air arrangement plan combined with the horizontal fuel rich-lean combustion technology, the altitude and horizontal directions' two-region combustion is formed to make boiler slagging-prevent and low NOx release. The test and numerical simulation are used to prove the scheme's feasibility, through analyzing the heat release rate in the burners' zone, the principle of choosing various zone's air excess coefficient is determined. Finally, the hot test illustrates the feasibility of the scheme.