Perovskite oxides have been considered as ideal electrocatalysts for water electrolysis since they are eco-friendly, abundant, and easy to be fabricated. However, their application in hydrogen evolution reaction (HER) is still limited because of relatively poor efficiency and stability. Herein, we report that a facile fabrication method, pulsed laser deposition, is employed to fabricate nanoscale LaCoO on nickel foam as an active electrocatalyst for HER. We find that in-situ surface reconstruction takes place in HER cycles, which enhances the HER activity greatly. By depositing additional NiO layer and annealing in H atmosphere, the catalytic performance and long-term stability of LaCoO can be further improved. As a result, the catalyst demonstrates a remarkable HER activity with a low overpotential of 180 mV at 10 mA cm and superb stability up to 50 h in alkaline media. Our work uncovers that the underlying phase transition in an alkaline medium and the interface engineering play critical roles in the improved HER activity of perovskite oxides. This work may provide insightful guidance to engineer perovskite oxides as electrocatalysts in the electrolysis of water.