Continuous basalt fibres (CBFs) produced directly from natural basalt seldom achieve adequate performance with high tensile strengths. Thus, formulation optimization is a key component of technological innovation in the field of CBFs. From this perspective, a series of experiments were designed to prepare a type of CBF using two natural forms of basalt. The average tensile strength of the fabricated CBF was 4111 MPa. Moreover, it is found that the amount of glass network modifier (Na2O + K2O) has a negative correlation with the tensile strength of CBF. By combining our results with past studies, two empirical formulas were proposed to quantify the relationship between viscosity (eta) and viscosity modulus (M eta) for basalt melts at 1300 degrees C and 1400 degrees C:eta(1300 degrees C) - 91.22971 + 16.06614e(1.25983M1) and eta(1400 degrees C) -30.57462 + 6.32023 e(1.18491 M eta). It was found that a value of M eta ranging between 2.2 and 2.6 is optimum for CBF production. We also established an important correlation between m Mu and mix compositions, which could be an essential criterion to evaluate the characteristics and production technology of CBF, including basalt beneficiation and formulation optimization.