For optimization of coolant conditions in DEMO blanket design, a two-dimensional (2D) nuclear-thermalcoupled analysis code, DOHEAT, has been modified. A striking feature of DOHEAT is to have a user-friendly interface that enables users to create an appropriate analysis model for different blanket concepts without much diffculty. In the modified DOHEAT, the coolant condition calculation module was added into the 2D thermal analysis module, and the temperature profile in the blanket was provided based on the nuclear heating rate profile and coolant temperature. In addition, numerical solution of simultaneous linear equation is changed from successive over relaxation (SOR) method to bi-conjugate gradient stabilized (Bi-CGStab) method for calculation speed-up. By improving DOHEAT, a series of blanket analysis including not only neutronics and thermal analysis but also coolant condition can be done. The modified DOHEAT allows to calculate the temperature change of the coolant along the cooling tube, and to evaluate the accurate temperature distribution of blanket.