The availability of tidal data in western waters of North Sumatra has not been optimal, tidal model is needed to represent the marine information. Regional tidal model (BIG model) was built from multi-mission altimetry data with response analysis method that was assimilated with 138 tide gauge (TG) data over Indonesian waters before 2018. The aim of the study was to evaluate the BIG model using TG data that were built after 2018, there were tidal data from TG.Barus, TG.Sirombu and TG.Batahan at 2019-2020. The research method is calculate the Root Mean Square (RMS), Root Sum of Squares (RSS), Root Sum of Squares of the In-phase and Quadrature (RSSIQ) and Discrepancy (D) of 8 harmonic constants (HC) M2,S2,N2,K2,K1,O1,P1,Q1. Also calculated the correlation between BIG model and predictions from TG data in January 2021. Analysis of HC from model and TG data showed that the largest to smallest RMSError were M2 0.039m, S2 0.015m, K1 0.012m, N2 0.008m, O1 0.005m, P1 0.004 m, Q1 0.004m and K2 0.003m. The value of D is 5.97% that indicating good tidal model reliability. The correlation value of BIG model and predictions from observational data TG.Barus is 98.73%, TG.Batahan is 98.74% and TG.Sirombu is 98.62%.