The invention discloses a polyamide elastomer foaming material and a preparation method thereof. The preparation method comprises the following steps: (1) extruding a mixture of a polyamide elastomer,a melt viscosity modifier, a pore nucleating agent and a foaming auxiliary agent by an extruder to obtain precursor for foaming; and (2) heating the precursor for foaming, then introducing a physicalfoaming agent to pressurize a reaction kettle, wherein the physical foaming agent is in a supercritical state, relieving the pressure after insulating and pressurizing and cooling and sizing the mixture to obtain the polyamide elastomer foaming material. The polyamide elastomer foaming material has the advantages of being light in weight, good in flexibility, uniform in size of pore, low in density of foaming material, good in foaming effect and the like. The melt viscosity modifier is introduced to change the melt viscosity and strength for the benefit of foaming for the characteristics of being relatively low in melt viscosity and strength of the polyamide elastomer and hard to foam. The preparation method is simple and suitable for being popularized and applied.