Based on the mass conservation equation, the calculation formula of the moisture content in the air-conditioned room without humidification in winter are deduced. Synthetically considering major influencing factors of the indoor moisture content, the criterion used to estimate the relative humidity of air-conditioned rooms without humidification in winter are established. Furthermore, the relative humidity in typical air-conditioned rooms without humidification in typical climate regions in winter is checked against the criterion. The main conclusions are as follows:the relative humidity of air-conditioned supermarket all around our country, restaurants and the multi-purpose halls of 3-star and below 3-star hotel in the "hot summer and cold winter" climatic region, movie theaters,office, the bedrooms and multi-purpose halls of hotel, restaurants in the "hot summer and warm winter" climatic region, and office, the bedrooms of 3-star and below 3 star hotel, the multi-purpose halls of hotel and restaurants in the "mild" climatic region can meet the required value without humidification. But, the relative humidity of air-conditioned movie theaters, office, the bedrooms and multi-purpose halls of hotel and the restaurants in the "cold" and "severe cold" climatic region, movie theaters, office, the bedrooms of hotels, and the multi-purpose halls of 4 star and over 4 star hotels in the "hot in summer and cold in winter", and movie theaters, the bedrooms and multi-purpose halls of 4-star and over 4-star of hotels in the "mild" climatic region can not meet the required value without humidification.