The invention relates to a comprehensive processing and utilization method of candied date processing wastewater. According to the invention, candied date processing wastewater is subjected to a quality-differentiated processing method. High-sugar-content wastewater is subjected to multi-effect evaporation, such that sugar is recovered. Therefore, sewage processing load is greatly reduced, and considerable economic benefit can be produced with the recovered sugar. Date washing water, ground cleaning sewage, and other domestic sewage are gathered and processed, at the same time, coal-fired boiler flue gas desulfurization is performed. Bio-desulfurization is carried out with organic pollutants in the sewage as a nutrient source, sewage is also processed to a certain extent, and water temperature is increased, such that subsequent biochemical treatments are facilitated. Biochemical treatment outlet water is subjected to biochar deep processing, and is subjected to microfiltration and RO (reverse osmosis) double-membrane processing, such that outlet water salinity is reduced, and boiler softened water requirement is reached. Therefore, date processing wastewater discharge amount can be further reduced, and consumption and discharge of softening acid and alkali for traditional boiler water can be further reduced.