Differential cross sections for the (40) Ca(n,) , and reactions are measured at neutron energies of 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5MeV using a double-section gridded ionization chamber and two CaF2 samples. Monoenergetic neutrons were produced through the (2) H(d, n)(3) He reaction with a deuterium gas target. A BF3 neutron counter was utilized to normalize the neutron flux among different measurements. The absolute value of neutron flux was calibrated using a U-238 sample. Angle-integrated cross sections for the (40) Ca(n,) , and reactions are obtained from the integration of the differential data. Model calculations are performed using the TALYS-1.6 code and general agreement is achieved between measurements and calculations. Then the total Ca-40(n,)Ar-37 cross sections are derived from the angle-integrated cross sections combined with the code calculations. Present results are compared with existing measurements and evaluations.