A method for evaluating reinforcement effect and efficiency of a filler on natural rubber based on particle size of bound rubber particles formed by the filler and natural rubber particle in a natural rubber latex, in which the natural rubber latex and the filler are mixed and diluted to obtain a to-be-detected emulsion, and an average particle size of bound rubber particles is measured using an instrument; a ratio of the average particle size to an average particle size of natural rubber particles in a pure rubber latex emulsion with the same concentration is calculated; the reinforcement effect of the filler on the natural rubber is evaluated based on the ratio; a function expression is established to derive a stress at definite elongation of various filler-modified natural rubber vulcanizates; and according to the function expression, the reinforcement efficiency of the filler on the natural rubber is evaluated.