We performed photometric, spectroscopic and orbital period investigations of ASASSN-V J015428.67+204247.2 (hereafter, J015428) for the first time. The light curves of VRI bands were obtained. Through the analysis of Wilson-Devinney program, J015428 was found as an A-subtype medium contact binary system with a low-mass ratio (q=0.129, f=26.8%). The atmospheric parameters were determined in spectroscopic analysis. In the orbital period investigations, we found that the orbital period of J015428 decreases at the rate of -7.13x10^-8^day/yr. And the long-term orbital period decrease is possibly due to angular momentum loss (AML). The absolute parameters was calculated with the photometric solutions and Gaia distance. Through the analyses of mass-radius and mass-luminosity diagrams of 54 contact binaries with the low mass ratios (0.096<=q<=0.15), the evolutionary states of low mass ratio binaries were investigated. The results by analyzing the energy transfer parameter indicated that energy transfer rate was a function of mass and bolometric luminosity ratio. We estimated the initial masses and the densities of two components and the age of the binary. The analysis of the orbital angular momentum supposed that J015428 may evolved from a short-period detached binary by AML. J015428 is in a stable contact stage at present.

Cone search capability for table J/PASP/135/E4201/tablea1 (Low mass ratio (0.096<=q<=0.15) contact binaries)