The invention provides a boiler energy saving and flue gas white smoke removal system, process and application. The boiler energy saving and flue gas white smoke removal system comprises a boiler, a denitration device, a rotary air preheater, an air mixing heater, a flue gas air heater, an electrostatic dust collector, a desulfurization tower and a chimney which are connected in sequence. The process comprises the following steps that ambient air is taken as a cold medium of the flue gas air heater and the air mixing heater, warm air of 80-140 DEG C generated by heat exchange of the flue gas air heater is taken as a cold medium of the rotary air preheater, mixed hot air over 160 DEG C obtained by heat exchange of the air mixing heater is introduced into a flue between the desulfurization tower and the chimney to heat clean flue gas, the flue gas sequentially passes through the rotary air preheater, the air mixing heater and the flue gas air heater for heat exchange to obtain flue gas of 85-120 DEG C, and the flue gas of 85-120 DEG C flue gas enters the electrostatic dust collector. The boiler energy saving and flue gas white smoke removal system is high in cost performance, can beused for preventing secondary blockage of ammonium bisulfate of a coal-fired unit, and can be applied to the coal-fired unit in the fields of petroleum, chemical engineering, metallurgy, electric power, ships, central heating, machinery, food, pharmacy and the like.