The present invention provides a warm-up operation control system for exhaust gas purification systems of internal combustion engines that improves the precision in warm-up operation control. When the rotation speed Ner of the engine E reaches the fully combusted state determining value Ner and the result of step 11 (S11) becomes "Yes", The engine ECU 9 calculates the total heat amount Qt st step 13 (S13) based on the amount of fuel consumed by the engine E. Then, the engine ECU 9 determines whether the total heat amount Qt has reached the first warm-up determining value Qth1 or not at step 17 (S17). If the result is "No", then the engine ECU 9 executes the warm-up operation in the first mode at step 18 (S18). When the total heat amount Qt reaches the first warm-up determining value Qth1 as the engine E warms up, and thus the result of step 17 (S17) becomes "Yes", the engine ECU 9 determines whether the total heat amount Qt is equal to or lower than the second warm-up determining value Qth2 at step 19 (S19).
