GT Works3 has a simulation function. 
When GT Designer3, included with GT Works3, is installed, the simulation function (GT Simulator3) is installed simultaneously. 
You can launch the function from GT Designer3 or independently from GT Simulator3. 
* To use GT Simulator3, a PLC CPU or controller simulator is required. 
* When using a controller simulator, prepare GX Works3, GX Works2, GX Simulator, or MT Developer2. (The required software depends on the PLC CPU to be simulated.)