Water-saving drilling system is a newest technique, which was developed to deal with the serious water scarcity for drilling in arid area and leaking formation. The water consumption in the drilling process was only 5%～20% of the original amount by drilling fluid local circulation at downhole. In the application of water-saving drilling system, in-hole drilling condition can only be judged by observing pressure change in pressure gauge on the surface with low precision. By study, the quantization of working condition in the hole could be observed through the surface pressure variation value and the preliminary theoretical mode was established to have more accurate judgment on in-hole drilling condition.