A system for detecting a filament for printing in three dimensional printing (3DP) which can automatically detect the presence of a filament includes a feeding device, a detection device, a driving device, and an indication module. The driving device drives the feeding device and the detection device detects and determines the normal presence of a filament from the feeding device. The indication module outputs a signal to correspond to the presence of a filament or otherwise. A 3DP filament detection method is also provided.