S形弯曲波导是集成光器件中不可缺少的部分。对比分析了常见不同形状的S 形光波导的传输损耗，找到了低损耗的余弦形状。在Marcuse 弯曲波导研究的基础上，通过曲线拟合方法，得到了几种近似计算损耗的公式。用Matlab 进行仿真，得到了损耗曲线。与传统低坡模型进行对比分析，以找到与实际值最接近的模型。结果表明，高斯曲线拟合方法可以更好地描述余弦形状波导的损耗。

S-shaped bend waveguide is indispensable to realize the lateral displacement and connections in the integrated optical devices. The transmission losses of different S-shaped waveguides are analyzed, and the lowloss cosine shape mode is found. On the basis of the previous Marcuse theoretical conclusions of bending waveguide, a curve fitting method is used and several approximate loss calculation formulas are obtained. By using the Matlab software, the loss graph is gotten. Then compared with the traditional low- slope model, the closest one to the theoretical model is found. The results show that the Guassian curve fitting method can better describe the cosine-shaped waveguide loss.