The purpose of the present paper istwofold. First, the projective Riccati equations (PREs for short)are resolved by means of a linearized theorem, which was known inthe literature. Based on the signs and values of coefficients ofPREs, the solutions with two arbitrary parameters of PREs can beexpressed by the hyperbolic functions, the trigonometric functions,and the rational functions respectively, at the same time therelation between the components of each solution to PREs is alsoimplemented. Second, more new travelling wave solutions for somenonlinear PDEs, such as the Burgers equation, the mKdV equation,the NLS+ equation, new Hamilton amplitude equation, and soon, are obtained by using Sub-ODE method, in which PREs are takenas the Sub-ODEs. The key idea of this method is that thetravelling wave solutions of nonlinear PDE can be expressed by apolynomial in two variables, which are the components of eachsolution to PREs, provided that the homogeneous balance betweenthe higher order derivatives and nonlinear terms in the equationis considered.