hello,everyone. I have figured this problem out recently after acquiring the basic knowledge of control theory. I used two port method to compute the loop gain transfer function and find there are four low frequency poles and one zero locating at origin due to feedforward path and feedback path respectively. Utilizing root locus method , I found that one pole goes to origin, one pole goes to infinite, and two poles bend to RHP after the interval loop is closed. So the pole generated by intermediate stage makes the circuit unstable. After I cancelled the intermediate stage,the circuit just behave like regular Ahuja' compensation way.
So thank you all for your suggestions.