The invention discloses a temperature-resistant and salt-resistant fluid loss additive emulsion which is prepared by four simple substances, namely acrylamide, N-vinyl pyrrolidone, dimethyl diallyl ammonium chloride and 2-methyl-2-acrylamide propanesulfonic acid, water, white oil, an emulsifier and an initiator. The invention further discloses a preparation method of the temperature-resistant and salt-resistant fluid loss additive emulsion. The temperature-resistant and salt-resistant fluid loss additive emulsion can resist temperature up to 220 DEG C and can resist salt to saturation; the emulsion contains an amide group, a sulfonic group, an amine group, cation ammonium and a six-membered ring, so that a polymer has very high temperature resistance; strong adsorption groups of the polymer can ensure that the polymer has a good adsorption effect to clay under the high temperature condition, and can ensure that the fluid loss additive emulsion has a better fluid loss effect at a high temperature; and in addition, the emulsion is good in repeatability and high in solution rate, and can be directly applied to a site.