The invention provide an answer simulation device and method for software testing. The device comprises an adaptation module; the adaptation module receives a test message sent by a tested system; when the format of the test message satisfies the preset data format, the adaptation module sends the test message to an analog control module, receives a reply message returned by the analog control module and sends the same to the tested system; if not, the adaptation module converts the test message into a first internal message according to the preset data format and sends the first internal message to the analog control module; the reply message is converted into a second internal message which is sent to the tested system; the analog control module searches for corresponding reply messages according to the test message or the first internal message from a preset case data table; the case data table stores the mapping relationship between the test message or the first internal message and the reply message set. Through the device and method, development and maintenance costs can be reduced, tests of any scene can be covered, test coverage range is enlarged.