The invention discloses a rapid predication method for fatigue limit of a dissimilar material spot-welded joint and relates to the technical field of fatigue reliability evaluation of a welding structure. The method comprises the following steps: determining a fatigue temperature-rising slope, corresponding to each load level, in a third phase; dividing the plurality of fatigue temperature-risingslopes according to an appointed rule, so as to obtain two groups of fatigue temperature-rising slope data; carrying out linear fitting on the two groups of fatigue temperature-rising slope data respectively to obtain two straight lines; taking a load level value corresponding to a crossed point of the two straight lines as a fatigue limit predicated value of the dissimilar material spot-welded joint, i.e., taking a load size corresponding to turning of the temperature-rising slope as a critical point of changes of a fatigue damage mechanism; predicating the fatigue limit of the dissimilar material spot-welded joint. According to the rapid predication method disclosed by the invention, rapid predication of the fatigue limit of the dissimilar material spot-welded joint can be realized and aresult has authenticity and reliability.