The invention provides a method for increasing well slots without stopping production on an offshore petroleum platform, comprising the following steps: (1) installing a subsea template (3) at one side of the bottom part of the original platform jacket (2); (2) removing a craw (13) on the subsea template (3); (3) inserting a steel pile (4) into a steel pile guide structure (12) of the subsea template (3), and then driving the steel pile (4) into the guide structure; (4) covering and fixing a steel pile sleeve (11) on the steel pile (4); (5) inserting a conductor tube (6) into a conductor tube guide structure (14), driving the conductor tube (6) into the guide structure and fixing the conductor tube with the guide structure together; (6) installing a connection structure (7) between the upper part of the platform jacket (2) and the conductor tube (6) of a new structure to integrate the original platform with a newly added well slot structure; and (7) installing a deck (8) on the original platform module (1), wherein, the deck (8) is positioned above the conductor tube (6). The method of the invention can greatly lower offshore operation time and construction cost, avoid shutdown during the offshore construction period and improve economic benefit for production.