In order to improve the accuracy of liquid level detection,the method was proposed by using the infrared technology with the conjugate gradient recognition algorithm.In view of the research problem,the identification model of liquid level detection was established in two-dimensional heat conduction.And on this basis,the direct problem was solved by using finite volume method.The quantitative detection for liquid level was proposed by using conjugate gradient algorithm.Influences of initial guess,the error of temperature measurement and heat transfer coefficient were analyzed by adopting numerical examples.The accuracy and adaptability of identification method were indicated through the identification results of numerical examples.At last the feasibility of identification method was proved through the experiment method.