The fluctuation of heat source influences the performance of adsorption cooling systems greatly in practical applications. This paper mainly investigates the cyclic characteristics of silica gel-water adsorption cooling system under the condition of general variable heat source, in order to explore the system characteristics and access the related operation strategies. In this work, all practical variable heat sources are regarded as the combination of two different changes: the slow time-varying change (long change) and the fast time-varying change (short change). Based on a transient model of adsorption chiller verified by experiments, the characteristics of adsorption cooling system under both the two types of changes are presented. With the slow time-varying change, the heat source variation rate is a key factor that influences the system performance greatly. And for the fast time-varying change, concentration is being focused on the influence on chiller desorption process. The methods to minimize this effect, such as to change desorption time, is discussed. Moreover, the water tank capacity plays a very important role under both slow time-varying and fast time-varying heat sources. The analysis in this work will eventually contribute to operation strategies under different conditions and methods to decrease the influence of heat source fluctuation. (C) 2009 Elsevier Ltd. All rights reserved.