A three-dimensional backscatter model for larch forest stands is described, with an emphasis on the construction of the tree model using Lindenmayer system (L-system). This model calculates the incoherent backscatter from larch forest composed of realistic tree structures. Using L-system, tree architectures were generated faithful to the real stand tree structure. The tree models simulated by L-system give exact position information of tree architecture and are used for calculating the probability density functions of tree components and improve the precision of radar backscatter model. Here, we define five major components of the radar backscatter model: direct crown backscatter, direct ground backscatter, direct trunk backscatter, multi-path interactions between crown and ground, and double-bounce from trunk-ground interactions. Total backscatter from a simulated larch forest is computed by incoherent summation of the components. In this paper, the 3D radar model is introduced based on a description of L-system model of larch tree. Next, the polarization radar returns of larch stands are simulated and analyzed at L-, C-, X- and P-band with different incident angles. This 3D larch radar model gives reasonable results of backscattering coefficients averaged over the entire larch stands.