An incoherent scatter radar (ISR) simulation system based on matrix laboratory (MATLAB) platform was introduced in this letter. The simulation system adopts a modular design concept and establishes a complete working link for ISRs according to the real ISRs principle of operation. Every ISR working stage that could have an effect on the ionosphere detection performance is simulated, such as signal transmission, ionosphere model, ISR spectrum, signal reception, and ionosphere parameters' extraction. The simulation platform can be used to perform incoherent scatter spectrum modeling and ionosphere parameters' extraction in various modes. In particular, the target ionosphere is modeled with the International Reference Ionosphere (IRI) model. An example is demonstrated in this letter, which shows that the simulation system could be helpful for the early design of an ISR and for designing the operation modes for ISRs. Furthermore, the simulation system has the potential to be optimized and upgraded to improve its efficiency and accuracy.