This study aims to identify milling force coefficients Kpq of CFRP. The Kpq(θ) function is written in the form of a Fourier series with respect to fibre cutting angle θ. Three new identification methods are presented. For Methods 1 and 2, Kpq at a given θ is identified using instantaneous and average force, respectively. For Method 3, Kpq(θ) function at full fibre cutting angles is identified using instantaneous force. The proposed identification methods are applicable to milling cutters with a non-zero helix angle. The principle of Methods 1 and 3 is the least squares method of instantaneous force, and the influence of condition number of normal matrix of milling force equation on the reliability of identification results is investigated systematically for the first time. For Method 1, normal matrices are well-conditioned at any axial depth of cut, ap, helix angle, β, and tooth number, Nt; for Method 3, ap, β, and Nt used for the identification process should avoid satisfying the condition that multiple teeth are involved in cutting simultaneously. At least 4, 12, and 4 experiments are required for Methods 1, 2, and 3, respectively. Validation results show that the error in average values of milling forces predicted using the three methods is only 18.7%, 5.05%, and 5.7% respectively.