The invention provides a method for forming optical compensating films, including: (a) providing a suspension containing clay; (b) adding a mono-functional acrylic oligomer of formula (I) in the suspension, wherein n1 is 2-25, R1 is C1-10 alkyl or H and R2 is H or CH3; (c) adding a water-soluble polymer in the suspension; (d) adding a bi-functional acrylic oligomer of formula (II) in the suspension, wherein n2 is 3-50, and R3 and R4 independently are H or CH3; (e) after the step (d), drying the suspension to form a film; (f) exposing the film under UV light to cure the film; and (g) stretching the film, wherein the film has only a negative C-plate property before the stretching and has both negative C-plate and positive A-plate properties after the stretching.