Polyamide amine flowing modifier for mineral oil based drilling fluid and preparation method of modifier

The invention discloses a polyamide amine flowing modifier for mineral oil based drilling fluid and a preparation method of the modifier. The modifier is prepared in such way that dimer fatty acid and polybasic amine are subjected to amidation reaction at 120-160 DEG C and then a reaction product is homogeneously mixed with a solvent; the content of dimer in the dimer fatty acid is greater than 78wt%; the polybasic amine is a homolog of polyethylene polyamine containing 2-5 amido groups; the molar ratio of the carboxylic groups in the dimer fatty acid to the amido groups in the polybasic amine is 1 to (0.2-1.2). The preparation process is fulfilled in a reaction vessel connected with a Dean-Stark receiver. The polyamide amine flowing modifier has high molecular weight and multiple active functional groups, can form multi-point adsorption, is hard to desorb from the surface of organic soil, and is continuously effective and stable in performance at high temperature; the preparation process is simple and reaction conditions are easy to control.