The Mg II core-to-wing ratio (c/w ratio) data is used to derive the solar extreme UV emission which brings a vital role in the creation of the Earth’s ionosphere region. A continuous Mg II c/w ratio data has scientific importance towards the analysis of the earth’s climate as well as for the solar chromosphere region. Various instruments of ESA and NASA satellites such as SUSIM, SOLSTICE, GOME, NOAA9, NOAA11 etc. measure Mg II c/w ratio data at different time scales but still some missing measurements are being reported. To fill those missing gaps, the current investigation has used the correlation analysis technique between Mg II and other solar indices separately. Our result establishes a highest correlation with 10.7 cm (2800 MHz) radio flux (F10.7) data in comparison to other solar indices during solar cycle 22 and 23. But for phase-wise correlation analysis, the correlation coefficient shows varying behavior during declining and rising phase of each solar cycle due to hysteresis of magnetic field inside the Sun. Also, the correlation coefficient of the linear regression model for Coronal Index vs. Mg II has a higher value than 10.7 cm radio flux vs. Mg II during maximum phase of each solar cycle. In the present investigation, the composite Mg II c/w ratio data is computed using a linear regression model with strongly correlated solar index data depending on time frame analysis of each solar cycle to achieve better correlation. Finally, a correlation analysis is also being performed between the computed composite Mg II c/w ratio and Bremen composite data and a fair correlation around 0.98 has been found. The computed series is also validated with other long-range solar indices data to verify different long-range trends that can reflect the actual nature of the Sun’s chromosphere region.