Creating lattice defects and alloying to produce strain effect in Pt-based bimetallic alloys are both effective methods to optimize the crystal and electronic structure and improve the electrocatalytic performance. Unfortunately, the principles that govern the alkaline hydrogen evolution reaction (HER) performance remain unclear, which is detrimental to the rational design of efficient Pt-based electrocatalysts. Herein, PtNi alloys with different Pt/Ni ratios and edge dislocations were synthesized, and the effects of Pt/Ni composition and edge dislocations on the alkaline HER electrocatalytic activity of PtNi alloys were systematically studied. Combined experimental and theoretical investigations reveal that tuning Pt/Ni ratio results in only 1.1 times enhancements in Pt mass activity, whereas edge dislocations-induced extra tensile strain on Ni site and compressive strain on Pt site further boost the alkaline HER intrinsic activity at all Pt/Ni ratios. Impressively, the introduction of edge dislocations in PtNi alloys could break the limit of alloying in boosting Pt mass activity and result in up to 13.7-fold enhancement, in the case that Pt and Ni contents are nearly identical and thus edge dislocation density reaches the maximum. Fundamental mechanism studies demonstrate that the edge dislocation strategy could make a breakthrough in facilitating water dissociation kinetics of PtNi alloys.