Apart from Wilmar, Martua and his elder brother Ganda Sitorus co-founded Gama Corporation in 2011, which run property, cement plant and others variety Business trough subsidiary Gama Land and Semen Merah Putih. Gama itself refer to its founder name Ganda & Martua (Ga-ma). Gama Corp owns 64 floor Gama Tower which is located at Rasuna Said - Jakarta, Indonesia. Gama Tower also known as the tallest building in Indonesia.

Martua along with Kuok Khoon Hong, the nephew of Malaysia's richest tycoon Robert Kuok, founded Wilmar International Limited and by 1991 he owned 7.100 hectare of palm tree plantations, and also build his own palm oil refinery in North Sumatra. The Wilmar International Business has grown rapidly; by 2013 Wilmar owns more than 50 other companies with 300 Manufacturing plants around the world. Martua also owns London skycraper Aviva Tower and a hospital in Medan, Murni Teguh Memorial Hospital, which is named after Martua's mother, Murni Teguh. The hospital was launched on 12 December 2012 (12/12/2012).

In 2014, Sitorus also formed a partnership with Roys Poyiadjis to create the largest biofuel power plant in Japan. The plant’s 20 year feed-in tariff is valued at $1.5 billion US dollars.