In this paper,it is described that the uncertainty of evaluation results of both DC gain and offset of the signal processing circuits of laser doppler velocimeters(LDV),which is by using the least mean square method.It is including the courses of analysis and evaluation of uncertainty of it.Some error sources of DC gain and offset evaluation are discussed,including the errors of signal source,the measurement errors and the linearity of device under test,the influence of quantization error of linear system,the environment influence and the others.Several main methods of decreasing the evaluation errors and evaluation uncertainty have been proposed.They are environment influence controlling, in order to decrease the signal uncertainty of source.In an example of experiment,the analysis and uncertainty evaluation results of both DC gain and offset of LDV by using the method in this paper is presented.The courses and conclusion of analysis and uncertainty evaluation of both DC gain and offset in this paper,can be applied to the uncertainty evaluation of measurement standards of both DC gain and offset,can also be used in the uncertainty evaluation of DC gain and offset themselves.