The invention relates to a compound type water retention agent for enhancing the germination rate of plants and preparation and application thereof, and belongs to the technical field of water retention agents. The compound type water retention agent comprises the following components in parts by mass: 6 parts of acrylic acid, 5 parts of acrylamide, potassium persulfate as an initiating agent accounting for 0.25%-0.35% of the total mass of the monomers, N-N' methylene bisacrylamide as an cross-linking agent accounting for 0.01%-0.03% of the total mass of the monomers, bentonite accounting for 25%-35% of the total mass of the monomers and sodium alginate accounting for 5%-6% of the total mass of the monomers. The preparation comprises the following steps: adding the acrylic acid, and mechanically stirring; adding deionized water, then introducing a NaOH solid, and regulating a PH value; slowly neutralizing by using the acrylic acid under stirring, and then respectively adding acrylamide, the cross-linking agent, the bentonite, the sodium alginate and the initiating agent; uniformly mixing, and then polymerization under airtight and static conditions, wherein a polymerized solid product is subjected to treatments, namely cutting, drying, crushing and the like. The compound type water retention agent disclosed by the invention achieves the water absorption rate by 500-750 times and the germination rate of seeds can be effectively increased.