The layer‐by‐layer liquid‐phase epitaxy (LBL‐LPE) method is widely used in preparing metal–organic framework (MOF) thin films with the merits of controlling thickness and out‐of‐plane orientation for superior performances in applications. The LBL‐LPE growth mechanism related to the grain boundary, structure defect, and orientation is critical but very challenging to study. In this work, a novel “in‐plane self‐limiting and self‐repairing” thin‐film growth mechanism is demonstrated by the combination study of the grain boundary, structure defect, and orientation of Cu₃(HHTP)₂‐xC thin film via microscopic analysis techniques and electrical measurements. This mechanism results a desired high‐quality MOF thin film with preferred in‐plane orientations at its bottom for the first time and is very helpful for optimizing the LBL‐LPE method, understanding the growth cycle‐dependent properties of MOF thin film, and inspiring the investigations of the biomimetic self‐repairing materials.