The invention provides a modified MoS2 nano material and a preparation method thereof. The modified MoS2 nanomaterial is comprised of a hydrophilic MoS2 nanosheet linked with hydrophobic alkyl amine chain, the hydrophobic alkyl amine chain is provided by an alkylamine compound. The modified MoS2 nano material provided by the invention can be formulated into a nanofluid i.e. oil-displacement agent at a lower concentration, and is applied to the tertiary recovery in oil recovery, thereby greatly reducing the environmental pollution in the tertiary recovery, reducing the cost and improving the oil recovery.