The invention provides a variable-displacement gear-type oil pump comprising a pump cover 1, a pump body 2, a driving gear 3, a driving shaft 4, a transmission gear 5, adjustment valve components 6, a driven shaft 7, a segmental sliding block 8, a driven gear 9, a whole-circle sliding block 10 and a spring 11, wherein the driving shaft 4 is mounted in the axial hole of the pump body 2 and the pump cover 1; the transmission gear 5 is in press fit with the outer end of the driving shaft 4; the driving gear 3 in interference fit is mounted in the middle of the driving shaft 4 to constitute a transmission component; the driven shaft 7, the segmental sliding block 8, the driven gear 9, the whole-circle sliding block 10 and the spring 11 constitute a variable component; the adjustment valve components 6 are arranged at intervals on the outer edge of the segmental sliding block which is separated from the driving shaft 4; and the transmission component of the driving gear 3 and the variable component of the driven gear 9 are arranged oppositely, and the transmission component of the driving gear 3, the variable component of the driven gear 9 and the adjustment valve components 6 can be combined into the variable-displacement gear-type oil pump. Accordingly, the invention can reduce the temperature of the lubricating oil, improve the lubricating performance of the engine oil, reduce the power loss of the engine, improve the efficiency and economical efficiency of the engine and reduce the production cost.