In order to estimate the direct and maternal additive genetic effects, and genetic correlations for number born alive trait (NBA) at different parities, the total of 31,312 litters in Yorkshire and Landrace pigs were collected from three National pig breeding fanns, including Binh Thang, Dong A and Thuy Phuong between 2001 and 2011 for this study. Results of statistical analysis using REML method and VCE6 software indicated that in case of using the multi-traits analysis model in which each parity as a separated trait, the direct additive genetic variances and heritability for NBA perfonned non-sinificult differences among parities, and also were down in comparison with the single-trait analysis model in which each parity as a replicated trait (0.010 - 0.038 and 0.114 respectively). While maternal additive genetic variances and heritability for this trait were very low (0.000 - 0.(08), common environmental variances and parameters were very significant for both of analysis models (0.013 - 0.128). Positive genetic correlations for NBA between the first as well as second parity and next parities were really high (0.412 - 0.969), while environmental and phenotypic correlations were very low for these cases (0.008 - 0.086 and 0.037 - 0.162 respectively). Therefore, the maternal additive genetic effect may not be included in the models of genetic evaluation for NBA and estimated breeding values can be applied to select the nucleus sows at the second parities for these pig populations.