In order to investigate the load transfer mechanism of composite joint for tower of cable-stayed bridge, a segment model test with a scale of 1:3 was carried out, and the strain distribution of composite joint and the relative slippage between steel and concrete structure were obtained. A three-dimensional finite element model was established based on the test model, the structural performance of shear connectors and the effects of main parameters of composite were further investigated. The analysis results show that the stress components are at a lower level. There is a small relative slippage between steel and concrete, and both of them can bear the force collaboratively. The bearing-plate and shear connectors are main load transfer components, and could share 40% and 60% of the load respectively. Vertical shear force is at a lower level within 0.6 times length of composite joint of bearing-plate, while the vertical shear force increases gradually within 0.6-1.0 times length. The length of composite joint and the distance of shear connector have a great influence on the shear force of connector, while the diameter of the hole and the thickness of bearing-plate display a less effect.