Abstract: In this paper we present a planning system for blocks-world domain. An important component of the system is a whole priority list, which guides the system in selecting suitable sub-goals in solving a given problem. This system is entirely different from the existing systems, which are primarily based on either backtracking or on invariant intermediate states or random selection of sub-goals. This system selects sub-goals in a systematic fashion. It generates a plan in polynomial amount of time, if there is no deadlock. The system has been implemented using Common Lisp. A graphical user interface is incorporated for the convenient specification of user inputs.