The abnormal heating of electrical contact is a common defect in power transformation equipment. Traditional heat prediction estimates temperature rise based on Joule's law, which has low accuracy and little practical reference. In this paper, based on the three-dimensional simulation model of force-electromagnetic-thermal coupling field, the actual contact state of the electrical contact and the influence of convection and heat dissipation with air are considered. The three-dimensional temperature field distribution of the electrical contact is calculated and analyzed. By comparing the temperature distribution of lap electrical contact and hoop electrical contact, it is found that the arc surface structure of hoop electrical contact has the advantage of optimizing the current distribution and suppressing the temperature rise. A predictive operation and maintenance oriented electrical contact thermal defect prediction method is proposed. The research results can provide simulation technical support for the digital twin model of equipment thermal defect prediction.