The invention discloses a phase-splitting and time-segmenting electricity stealing investigation method. The method comprises the following steps: acquiring operation data of a power grid; selecting regions where the line losses are larger than a set value; checking data of three-phase electric energy meters except gateway meters, and selecting a specific electricity stealing judgment date; obtaining single-phase electric energy meters under each phase line through screening; obtaining the total electricity quantity of all the single-phase electric energy meters under each phase line through statistics; calculating the line loss of each phase line; selecting the phase lines, of which the line losses are larger than a set value, as target phase lines for electricity stealing investigation;if the line loss of each phase line is larger than a set value and the total electricity quantity of all the single-phase electric energy meters under each phase line is larger than a set value, segmenting an analysis period and calculating the line loss of each time segment; and carrying out the electricity stealing investigation on the time segments, of which the line losses are larger than a set value, and carrying out the electricity stealing investigation on the phase lines, of which the line losses are larger than a sixth set value within the time segments, of which the line losses are larger than a fifth set value. The method disclosed by the invention has the advantages that an electricity stealing investigation scope is smaller, so that electricity stealing positions can be quickly determined, and higher efficiency can be achieved.