A POSS modified polyacrylate fluorine-free waterproofing agent includes following components: 1-10 wt % of a functionalized POSS monomer, 2-20 wt % of methyl methacrylate, 3-26 wt % of butyl acrylate, 1-10 wt % of a long-chain acrylate monomer, 0.5-3.5 wt % of an initiator, 0.5-4 wt % of a reactive cationic emulsifier, and 50-80 wt % of deionized water. A method of preparing a POSS modified polyacrylate fluorine-free waterproofing agent is also disclosed.