As the cost of executing and maintaining a large test suite is always expensive, many test suite reduction techniques have been proposed and some empirical studies of test suite reduction techniques have already been reported. The aim of this paper is to provide a guideline for choosing the appropriate test suite reduction techniques for Boolean specification-based testing. Four typical heuristic reduction strategies: G, GE, GRE, and H??are introduced to be compared empirically. Furthermore, testing requirement optimization is combined to enhance these four reduction strategies. This paper presents the empirical evaluation of these reduction strategies based on a set of Boolean specifications from TCAS II.