Translating is a cross-cultural problem-solving activity. Translating problems refer to the inter-subjective difficulties (irrelevant to translation competence and technical conditions) which every translator encounters in their translation activities. Translating problem is a central concept in translation studies. However, it is still in the “gray zone” of the field. In the light of Activity Theory, translating problems can be classified and the mechanism of translators’ decision-making in solving the problems can be further explained by means of an analysis into the process of translation activity actualization, which is constrained by the multiple stratified contextual factors. In a translation activity, a translator would be faced with the conventional and textual problems caused by the ‘condition’ of operation act. S/he may also be challenged by the situational and professional ones resulting from the incongruity between the “goal” of translation action, operation condition and the “social rules” governing the translation activity. S/he would respectively deal with these problems in compliance with the source text function, situational translation function, translation norm and conventionalized translation function.