A Chinese deliveryman cyclist mowed down by an MTA express bus was a victim of the Second Avenue subway-construction chaos on the Upper East Side, his distraught family charged yesterday.

Relatives of Qi Ming Weng, 26, of Brooklyn, also questioned why the bus driver didn’t stop after hitting the deliveryman as he rode on an electric bike on Second Avenue near East 96th Street.

“I don’t believe the driver. He should have stopped,” said Wendy Weng, 48, the victim’s aunt.

The out-of-service bus heading to its route kept going. The driver, whose name was not released, was apparently unaware he had struck someone, cops and witnesses said.