Roulin $\mathit{et}$ $\mathit{al}$ (1988), in one of their experimental papers, have presented a study of field-dependent entropy of high-purity YBa2 Cu3 O$_{7−\delta}$ (YBCO) as a function of oxygen deficiency. In order to explain their experimental results, we have used phenomenological GL-theory of anisotropic HTSCs in the London limit in line with of our earlier paper (Pattanaik $\mathit{et}$ $\mathit{al}$, Physica B405, 3234 (2010)). Moreover, to account for the applicability of the theory at high field, we have incorporated the effect of vortex overlapping in the London theory done by Nanda (1995). Here, we have presented the variation of change in entropy (𝛥S) with magnetic field for different oxygen deficiencies $\delta = 0$, 0.04, and 0.06. On comparison, we found that our results are in good agreement with the experimental data of Roulin $\mathit{et}$ $\mathit{al}$ (1988). The variation of penetration depth (𝜆) and anisotropic ratio of effective masses (𝛾) with concentration is also presented.
