The purpose of the present study was to evaluate the capability of Monte Carlo N-Particle Transport Code System-eXtendend (MCNPX) Monte Carlo code on investigation the water equivalent different solid phantoms and their shielding parameters and also define a standard input code in MCNPX code for future studies on related investigation field. For this purpose, we calculated the radiation mass attenuation coefficients of investigated solid phantom samples. Materials and Methods: To obtain the features of investigated solid phantoms, MCNPX (version 2.4.0) general purpose Monte Carlo code has been utilized for simulation studies. The material definitions of 12 different solid phantoms such as elemental mass fractions, density, geometrical shape have been done, seperately. To observe the photon transmission of selected materials, Lambert-Beer law has been utilized according to obtained output results from simulations. Results: The obtained values for mass attenuation coefficients of selected solid phantoms have been agreed not only with standard XCOM data but also with previous experiemental and simulation studies. Thus, our input file has been considered as a validated input for the next calculations. The results showed that, MCNPX is more consistent than FLUKA code with experiemental and standard data in the low energy region. On the other hand, the results also showed that water equivalances of some solid phantoms are quite similar with water phantom. Conclusion: It can be concluded that MCNPX code can be employed for solid phantom studies. It can be also concluded that, present study would be very useful for use of standard simulation geometry for medical physics and radiation dosimetry applications with solid phantoms.