Demolition work is being carried out on the former Six Acres day centre that will house part of the new supermarket.
The existing Roman Road premises will close on Friday as work proceeds over the coming seven months.
The new, bigger store is then set to open in November.
It is the second time Lidl has demolished a store in Taunton to replace it with a larger one.
The previous store in Wood Street was bulldozed after the company relocated to Castle Street.
Lidl has issued an image (below) of how the new Roman Road store will look once completed.
READ MORE: Work starts on new Lidl store in Taunton