No. As with all Buddhist traditions, the main practice of the New Kadampa Tradition (NKT) is going for refuge to the Three Jewels of Buddha, Dharma (Buddha’s teachings and the inner realizations gained from practicing these teachings), and Sangha (the spiritual community).
As with all Mahayana Buddhist traditions, the main practice of the NKT is also generating the supreme good heart, bodhichitta (the wish to attain enlightenment to liberate all beings permanently from suffering and its causes).
Because NKT practitioners also practice the Tantric path according to the instructions of Buddha Vajradhara and Je Tsongkhapa, they rely on the Guru (Spiritual Guide), Yidam (Tantric personal Deity), and Dharma Protector in order to fulfil their bodhichitta wish to attain enlightenment. These are manifestations of the Three Jewels, as explained by Je Tsongkhapa.
The main Dharma Protector of the NKT is the Wisdom Buddha Dorje Shugden. It also relies on other Dharma Protectors such as Mahakala, Palden Lhamo, Kalarupa, and Kinkara.
While relying upon Dorje Shugden is very important to those who are trying to uphold Je Tsongkhapa’s tradition, and especially the Ganden oral lineage, it is not the main practice of the NKT.