The victim was working for Chesterfield-based groundworks subcontractor Melfort Construction Services on the site where Lindum Group is main contractor.
It is understood the man was trapped under an overturned digger.
Lincolnshire Police said: “We can confirm that a 23-year-old Nottinghamshire man died at the scene.
“Next of kin have been informed and we are now working with the HSE to establish the circumstances of this tragic incident.”
Lindum Group company secretary Herman Kok said: “We are extremely sad that an employee of one of our subcontractors has lost his life following an incident on one of our construction sites earlier today.
“Our thoughts go out to his family, friends and colleagues at this awful time.
“We will be working closely with the HSE and emergency teams as they carry out their investigations into the tragic event and we will be supporting Lindum employees and other site personnel who have been affected.
“The victim was an employee of Melfort Construction Services Ltd, a civil engineering specialist based in Chesterfield, Derbyshire.”