The invention provides an automatic checking method of an analogue input merging unit. The method is capable of automatically completing metering error measurement and evaluation on the analogue input merging unit by use of a three-phase programmable voltage/current standard source with zero-crossing synchronous clock output, an error calculation unit and a control display unit. The automatic checking method is characterized in that the control display unit is arranged to control the standard source to output a voltage/current value and a synchronous clock signal both meeting certain requirements, so that other signal input ends, outside a detection channel, of the tested merging unit are set null, the error calculation unit obtains the channel number configuration of the tested merging unit and the transformation ratio configuration information of a pre-transformer by use of an analytical calculation standard sampling value and a tested sampling value, and thus realizes the channel configuration of the tested merging unit and automatic detection of the transformation ratio of the pre-transformer. The automatic checking method effectively solves the problems of low detection efficiency, high labor intensity, inconvenient equipment carrying and the like of the analogue input merging unit, and has the advantages of simple and practical method, high reliability and the like. The automatic checking method is applicable to the detection of the analogue input merging unit of an intelligent substation.