The invention provides a water-retaining liquid suspension fertilizer and a preparation method thereof. The water-retaining liquid suspension fertilizer is prepared from, by weight, 27-29 parts of humic acid, 6-8 parts of a nitrogen fertilizer, 5-11 parts of a phosphate fertilizer, 7-8 parts of a potash fertilizer, 1-2 parts of a boron fertilizer, 0.5-1 part of EDTA-Fe, 0.5-1 part of EDTA-Zn, 0.5-1 part of EDTA-Mn, 7-10 parts of a water retention agent, 3-5 parts of tea stems, 1-2 parts of a wetting and dispersing agent, 1.6-3 parts of an emulsifier, 1-4 parts of a thickener, 0.5-1 part of a preservative and 0.5-1 of an anti-tackiness agent. The water-retaining liquid suspension fertilizer has the advantages that a large amount of elements such as the humic acid, nitrogen, phosphorus and potassium are contained, trace elements such as boron and zinc are also added in time; a water retaining agent itself has a water absorption effect, can absorb and store water when the content of soilwater is high, and can release water when the content of the soil water is low, thereby achieving the water-saving and water-retaining effects.