The invention provides a simulation experiment system for staged fracturing or simultaneous fracturing of horizontal wells. The system is used for performing fracturing simulation on a cubic artificial rock sample and comprises fracturing simulation assemblies, stress loading devices and fracture monitoring devices; each fracturing simulation assembly comprises a simulation wellbore, a liquid injection pipe and a position adjusting device; the simulation wellbores are located inside the artificial rock sample; the liquid injection pipes are located in the simulation wellbores; and at least two simulation perforations which are equal in number and different in position are formed in each simulation wellbore and each liquid injection pipe. Positions of the liquid injection pipes are controlled by the position adjusting devices, the communicating sequence of the simulation perforations in different fracturing sections is realized, and the different fracturing sections are fractured respectively. The simultaneous fracturing process of the two horizontal wells can be simulated by the two fracturing simulation assemblies. The simulation experiment system can simulate interference phenomena among fractures during staged fracturing of the horizontal wells or simultaneous fracturing of the two horizontal wells, and an experimental method is provided for understanding of hydraulic fracture propagation rules and fracture shapes.