In order to solve the problem about optimal sensor placement in bridge structure health monitoring, taking the simply supported steel truss bridge as the study object, the improved optimal sensor placement method based on energy coefficient-effective independence method was proposed, which compensated the weaknesses of the traditional methods. Reflecting the coefficient of the node freedom modal strain energy, the proposed method can modify effective independence method which reflected the maximum linear independence, and further optimize the sensor placement designs. The analysis of an example shows that the evaluations of the designs were good, and the method can ensure the orthogonality of the measurement vibration pattern vector, and can also ensure the accuracy of the expanded order vibration and has better anti-noise ability, which is an ideal method appropriate for the bridge structure.