Surface reflectance model of forests with a consideration of interactions among trees and land surface including grasses in terms of multiple reflections by means of Monte-Carlo simulations together with experiments is proposed. The Monte Carlo method statistically simulates the paths of photons inside the atmosphere and the forested area to clarify the behaviors of individual photon. The radiance on ellipse and cone types of canopy calculated agreed well with the measured. Influences due to shape of the trees, trunk tree distance, and ratio of horizontal and vertical size of the trees and so on to the parameter estimation are clarified with the experimental results. It is found that a few to more than 10% of influence due to multiple reflections among trees are anticipated. The potentialities of the code are then depicted over different types of forests including coniferous and broadleaf canopies.