On a tip-off, police laid a trap at Kapurbawdi area and sent a decoy customer to buy venom from them, said senior police inspector J S Kadam.
Police seized over a half litre of the venom from their possession.
According to police, the venom commands the market rate of Rs 1 crore.
The accused are identified as Prakash Nirmale (23), Santosh Patil (22), Ravindra Sutar (25) and Nilesh Patil (25), police said.
They are booked under sections of Wild Life Protection Act, 1972, Kadam said.
