I have two model . all details of two model is similar, dimensions , boundry condition type and value .but answers of models are different . models are drawing and meshing in gambit and analysis in fluent

The meshing may be different. Check the number of cells in both. The mesh has to be made finer and finer till there is no more changes in the answers. Then we have a grid independent solution. We are supposed to reach there to get a correct result.

if you using different type of fluent versions, there will be some change in answer. And also number of cells will differ the answer.