Analytical method for curved optical waveguides plays an important role in dealing with integrated optical devices based on curved optical waveguides. It helps us not only in understanding physical mechanism of waveguides deeply but also in improving performance of existing integrated devices and designing novel elements. Bend loss of curved optical waveguides is always a problem to be focused on. In order to reduce bend loss of curved optical waveguides, a number of strategies have been used. In this paper, we proposed a new method to analyze curved optical waveguides, which combined the conformal transformation method with ray optical method. An intuitionistic physical image of bend loss in optical waveguides was founded from this point of view, then the reason of bend loss was clearly shown. Accordingly, a new strategy to reduce bend loss in curved optical waveguides was given. Compared with general strategies of modifying the refractive indices whatever in core or cladding, the present strategy is totally deferent. This strategy is beneficial to decrease the radiation of propagation modes in curved optical waveguides by increasing the thickness of curved waveguides. Especially, it is more effective in situations that the radius of curvature of the waveguides and the refractive indices of materials were set beforehand. Software simulation based on BPM was used simultaneously as supplemental verification of this new strategy. Moreover, as an example with this strategy, a special design of ring waveguides structure was given.