Abstract: Power substation area's line loss management is a long-term important task for power supply enterprises. High line loss rate and negative line loss rate are common problems in the process of line loss management. In the actual work of line loss control in substation area, electricity stealing is one of the important reasons for the increase of line loss rate, which is also a relatively common phenomenon. but the problem of negative line loss rate caused by electricity stealing is relatively rare, and is easy to be ignored. This paper analyzes an actual case which causes negative line loss rate in substation area.