I am learning the plink software now. I wondering what command can caculate the OR value of additive model with plink. Is it the ADD value in the result of the "plink --logistic" command？or the ADD value in the result of the "plink --logistic--genotypic" command？or other else? Thank you very much.

At the plink homepage: The TEST column is by default ADD meaning the additive effects of allele dosage. Adding the option --genotypic will generate file which will have two extra tests per SNP, corresponding to two extra rows: DOMDEV and GENO_2DF which represent a separate test of the dominance component or a 2 df joint test of both additive and dominance (i.e. corresponding the the general, genotypic model in the --model command).

I can understand this sentence "The TEST column is by default ADD meaning the additive effects of allele dosage." is response to the forward command-"plink --bfile mydaya --logistic", or response to the backward command-"plink --bfile mydaya --logistic --genotypic".