The invention relates to a synchronous grouting visual simulation testing system for a quasi-rectangular shield. The testing system comprises a transparent simulation segment, an outer sleeve, a power device, a grouting device and pressure detection devices; the simulation segment is arranged in a soil body, and the outer sleeve is arranged on the simulation segment in a sleeving mode and provided with grouting holes; the power device is connected with the outer sleeve, and the power device pushes the outer sleeve to move so as to enable a grouting gap to be formed between the simulation segment and the soil body; the grouting device is connected with the grouting holes and used for grouting slurry into the grouting gap through the grouting holes; the pressure detection devices are installed on the outer wall face of the simulation segment and used for measuring grouting pressure data and soil pressure data. According to the synchronous grouting visual simulation testing system, the transparent simulation segment is arranged, the slurry state of the quasi-rectangular shield in the pushing grouting process can be visually observed and simulated, pressure changes in the grouting process can be directly measured, and test analysis can be well conducted.