To deal with the problem that 4SY-1.8 rape windrower worked with large frame amplitude because of the random and uncertain exciting force of the reciprocating cutter the movable knife, the causes were analyzed that led to different vibration amplitudes in various parts of the cutting table. Based on the characteristics that the cutter drive shaft was driven by hydraulic motor and its speed was infinitely adjustable, the torque and the power consumption of the cutter drive shaft were tested. The top twenty natural frequencies and mode shapes of the frame were obtained by modal analysis simulation. The correctness of modal analysis simulation was verified by hammering method. The functional relationship between the cutter drive shaft torque, the cutter shaft rotational speed, the first order total deformation values of modal analysis and each test point average peak vibration displacement were fitted by RBF neural network. Neurons weights of each layer were obtained and the correctness of the RBF neural network model was tested. Results show that the fitting relations between frame test point average peak vibration displacement and cutter shaft rotational speed conformed to the exponential distribution and the correlation coefficient were higher than 0.944. 