The invention relates to an indoor testing device for simulating grouting pile end post-grouting and a testing method. The indoor testing device comprises an air compressor, a grout storage tank and a model pile which are connected in sequence. A connection pipeline of the air compressor and the grout storage tank is provided with a pressure regulating valve and a pressure gauge. The top of the grout storage tank is provided with a flange top cover, and the bottom of the grout storage tank is connected with the model pile through a grout inlet pipe and a grouting valve. The model pile is inserted into a model groove. Compared with the prior art, the indoor testing device for simulating grouting pile end post-grouting and the testing method can be used for simulating a grouting process of in-situ grouting pile end post-grouting and is capable of well reflecting actual process procedures of pile end post-grouting, achieving pile end post-grouting of large-size model grouting piles of different soil layers and controlling the grouting pressure and the grouting quantity. By means of the testing result of the indoor testing device and the testing method, the actual working properties of foundation piles subjected to pile end post-grouting can be well reflected, revealing of a grouting mechanism of pile end post-grouting is facilitated, and a reference base is provided for design, construction and the like of pile end post-grouting of an actual pile foundation project.