The two women were approached by three hooded men wearing terrifying Halloween-type masks as they opened up the centre on Wednesday 7th November.
One woman suffered minor injuries and bruising during the ordeal, in which the men grabbed her and her colleague.
But the women heroically fought off the intruders and managed to raise the alarm.
Nothing was stolen from the antiques centre - the largest in Europe - which is spread across three buildings on the former RAF base at Hemswell Cliff, near Gainsborough.
Detectives are now hunting for the three men who escaped out of a window and fled across a field behind the centre in a blue 4x4 vehicle.
“Despite being outnumbered by these three hooded men in dark clothing who were wearing scary masks, the two women put up brave resistance and even managed to operate the alarm system,” said Detective Constable Glenn Wright of Lincoln CID.
“Although the whole incident only lasted a couple of minutes, it was a very nasty, scary situation.”
He described how the members of staff had arrived for work at 9.45am on Wednesday 7th November and were unlocking one of the buildings.
“The men were waiting within the building, having broken in at some point,” said Det Con Wright.
“We assume their intention was to commit a robbery.”
“The women were approached by the men who grabbed them but they managed to get away and raise the alarm.”
“It was a determined and organised attempt. But for the bravery of the two female members of staff who knows what could have happened.”
It is thought the robbers had been intending to steal jewellery.
Police now want to speak to anyone with information on the people responsible, or the vehicle they escaped in.
They also want to hear from anyone who saw suspicious activity in the area between Tuesday evening and Wednesday morning.
The trio were described as white, all wearing dark clothing and plastic Halloween-type masks. One mask had gold colouring around the eye slits.
“We are also trying to trace a man who was on the phone to one of the women at the time of the incident,” added Det Con Wright.
“He was inquiring about an oak table. He may have heard something and be able to help our inquiry.”
Anyone with information should call Det Con Tina Kennedy of Gainsborough CID via the non-emergency number 101.
Quote incident number 111 of Wednesday 7th November.
Robert Miller, who owns Hemswell Antiques Centre, said his staff were ‘very shocked’ by what had happened.
“They were very brave in what they did,” he said.
“Unfortunately this is a sign of the times. It was frightening for those involved but we will stand strong and won’t let this happen again.”
He added: “Nothing was taken but we have got to catch these people.”