Police in California have arrested a man accused of being drunk and knocking down a robot that was built to prevent crime.

The 300-pound robot named K5 spins and occasionally whistles, acting as security to the technology store next to it in the Mountain View area.

"I think this is a pretty pathetic incident because it shows how spineless the drunk guys in Silicon Valley really are because they attack a victim who doesn't even have any arms," Mountain View resident Eamonn Callon said.

Police say Jason Sylvain, 41, knocked down the Knightscope droid while it was patrolling the car park.

"I think this is probably a first for us, but we are no strangers to technology," one woman said.

The robot referred to as K5 suffered some scratches, but after some TLC, it is back on the street protecting the neighbourhood.

The co-founder said it's a testament to the technology that police caught the aggressor and booked in him jail.

Police said Sylvain faces prowling and public intoxication charges.