Two welds of lock joint were processed by laser deep penetration welding, and X-ray digital radiography (DR) inspection and micro-computed tomography (micro-CT) inspection were carried out, the depth distribution characteristics of pores in lock joint by laser welding were researched. Firstly, the DR image of pores distribution in plate-like lock joint by laser welding was analyzed. Then, the three-dimensional structure of the lock joint weld was reconstructed by micro-CT, 134 and 126 pores were extracted respectively from lock joint welds of No.1 and No.2, and the pore diameter was quantitatively analyzed. The pore depth distribution characteristics were analyzed by the position of the pore center, and the pore distribution information within and outside the effective welding depth range were obtained. The results showed that most of the pores in the two lock joint welds were less than 1 mm in diameter, and 73.1% and 64.3% of the pores in No.1 and No.2 lock joint welds were distributed in the same depth range. Finally, in accordance with the X-ray acceptance standards of company’s laser weld, based on the X-ray DR inspection results and micro-CT inspection results, both lock joint welds were rated as grade Ⅲ.