The invention discloses a foaming material for a gas field foam discharging agent, a slow dissolving foam discharging agent, and a preparation method of the slow dissolving foam discharging agent, and belongs to the technical field of the oilfield chemistry. The foaming material comprises, by weight, 1 part of Sapindus mukurossi Gaertn extract, 0.03-0.1 parts of fatty alcohol polyoxyethylene ether AEO18 and 0.01-0.1 parts of lauric diethanolamide. The foaming material can be obtained by compounding the above three components, can mutually enhance surface active substances in the foaming material, improves the stability and environmental disturbance resistance of foams, improves the biodegradability of a surfactant, and reduces the toxicity of the foam discharging agent and the pollution of the foam discharging agent to the environment. PVA and an enteric acrylic resin are added as dressing materials, so the dissolving rate of the foaming material in water can be effectively controlled, thereby the foam discharging agent obtained by using the foaming agent is slowly dissolved in water, has a strong salinity resistance and a strong condensate oil resistance, has a very strong secondary foaming ability, has good compatibility with drugs comprising methanol, a corrosion inhibitor, a scale inhibitor and the like, and does not chemically react with gas or liquid components.