Objective: To observe and compare the effects of multi-patch biopsy under conventional white light imaging endoscopy (C-WLI) and precise targeted biopsy under magnifying narrow-band imaging endoscopy (M-NBI) on the endoscopic submucosal dissection (ESD) of early gastric cancers and intraepithelial neoplasias. Methods: According to the way of selecting biopsy specimens, patients were divided into C-WLI and M-NBI groups, 20 cases. The ESD operations of the 2 groups were compared quantitively. Results: The mean frequency of biopsy in M-NBI group was ($1.00{pm}0.00$), obviously lower than in the C-WLI group ($4.78{pm}1.02$) (P<0.01).The average total number of selected biopsy specimens was also fewer ($1.45{pm}0.12$ and $7.82{pm}2.22$, respectively, P<0.01). There was no significant difference in the time of determining excision extension, marking time and the time of specimen excision of 2 groups during the ESD (P>0.05), whereas submucosal injection time, mucosal dissection time, stopping bleeding time, wound processing time in the M-NBI group were significantly shorter than in the C-WLI group (P<0.01). Conclusion: Precise targeted biopsy under M-NBI can obviously shorten the time of ESD operation, with small quantity of tissues but high pathological positive rate.