The invention discloses an extensible test platform based on a tunable semiconductor laser absorption spectrum technology. A signal generating module is connected with a laser driving module; the laser driving module is connected with a laser signal generating module; a laser signal receiving module is connected with a prepositive amplification module; the prepositive amplification module is connected with a digital phase lock amplification module; the digital phase lock amplification module is connected with a data collecting module; the data collecting module is connected with a control module; the control module is connected with the signal generating module, the laser driving module and the digital phase lock amplification module in a control manner; the laser signal receiving module and the laser signal generating module are in opposite arrangement, and are arranged at two sides of a gas chamber. The extensible test platform has the advantages that the experiment efficiency can be improved; the development experiment cost of instruments and the work intensity of experimenters are reduced. The extensible test platform is suitable for experiments of instruments for various kinds of gas to be detected.