To trap ghosts by shrinking down their size.
The Ghost Goblin is an Ectoplastic Holographic Laser Perimeter. According to Eddie Spenser Jr., it's purpose was to trap ghosts in a net-like substance. The device also works as a shrink-ray.
When Tracy the Gorilla gave a demonstration of it's use inside Ghost Command, he made a lamp that hung from the ceiling shrink and disappear into nothingness. Later, Jake Kong Jr. used the Ghost Goblin to trap Count Grumpette in it's beam. he then shrank the count and pulled him towards him with the same beam. By this time, the Count was small enough for Kong to hold him in one hand.
The Ghost Goblin was first used in the episode Going Ape.