In view of the difficulty in precisely controlling the pre-stressed concrete track beam and the operation noise and vibration of all steel structure track beam，a new type of assembled steel-concrete composite track beam connected by group nails was developed. The steel beam and concrete slab were prefabricated separately and installed by group nails. The experimental model of test beam was made according to 1:3 geometric scale. The natural frequency，load deflection curve and section height strain curve of steel beam and composite beam before and after assembly were calculated by finite element method and measured by lab testing. The results were compared with the theoretical results of equivalent stiffness of steel-concrete composite without interface slip，so as to obtain the stiffness adjustment coefficient under different working conditions and verify its accuracy and applicability. The results show that：the measured load stiffness adjustment coefficient curve exhibits nonlinear behavior with the increase of the test load，the stiffness adjustment coefficient first increases and then decreases； the steel-concrete composite section does not fully conform to the assumption of plane section，and the nonlinear characteristics of concrete slab under large load is more obvious；based on the stiffness adjustment coefficient，the theoretical value and the finite element calculation value were modified respectively，and the error between the frequency and the measured value is between 2.2 % and 4.0 % ，and the stress error between 8.0 % and 23.8 % . The calculation and design of this kind of structure can be guided and simplified by using the stiffness adjustment coefficient in practical engineering.