Information Systems (or computer-based information systems) have begun to turn simplicity to complexity and turn hard-to-use to easy-to-use. However, effectiveness and efficiency on computer-based information systems is not satisfying yet. In order to keep information ecology (which has been complex and which information systems ecology belongs to) balance, computer-based information systems ecology and effectiveness and efficiency on computer-based information systems should be paid more attention. The paper mainly analyzes computer-based information systems problems from an ecological perspective to make people scientifically and comprehensively understand information systems and seek for better solutions to development and use of information systems. Computer software ecology is the most complex among the four ecologies (computer software ecology, computer hardware ecology, computer talents ecology and information surroundings ecology which information systems ecology involves), and has bigger effect on information systems ecology and information ecology than the other three. Computer software ecology is mainly discussed in the paper.