The accurate data on the second virial coefficient for refrigerant R41 are necessary for technologically important gases and liquid e.g. fluoromethane. Data were obtained from results of experimental and theoretical thermodynamic investigations of the refrigerant in question. While making an approximation of the second virial coefficient values the thermal dependence equation of the coefficient was changing. The simple equation for second virial coefficient is presented as function of temperature. In the experimental temperature range from 0 oC to 190 oC the deviations between the values of the second virial coefficient derived from experimental data and calculated using this equation are generally less than 1,5%.