The site will be open during the New Zealand Archaeological Association Conference, being held on the island, on August 29.
Rakiura Heritage Centre Trust building committee chairwoman Margaret Hopkins said it still had a lot of work to do on the site, but it would display the museum's Lockerbie collection during the event.
''The centre will not be ready, but we will lay out the collection and [visitors] and locals can come and look at it.''
The 509sqm centre in Oban was expected to open in April 2020 and Ms Hopkins said the feedback from the community so far had been positive.
She was hoping to combine the Maori and pakeha stories at the site and urged to the community be involved.
''We are quite excited to tell our story well. We currently have some objects in the old museum, but I don't think it shows the stories as well as they could be [shown].''
Ms Hopkins believed the new centre, which would incorporate environmentally friendly design features such as solar power generation and water collection, would be an important asset for the island.
Everybody saw the benefit for the tourism, especially on bad weather days, because there were not a lot of other indoor things to do on Stewart Island.
Much like the old museum, the heritage centre would be run mostly through the efforts of 12 volunteers, but she hoped to be able to employ one person so the museum, which is open daily from 10am to 1.30pm, except Sunday (12pm to 2pm), could be open over longer hours.
She said the challenge of the new museum was figuring out what items would be put on display, as a big part of the collection had been in storage.
''Stewart Island is special in so many aspects and we will be able to celebrate this.''
