The invention relates to a multi-parameter time-varying robot spraying method which comprises the following steps: firstly, establishing a free-form surface multivariable spraying model which uses flow of a spraying gun, a spraying distance and a spraying speed as model independent variables; then discretizing an original spraying path into a plurality of sections of minute sub paths, distributing initial values of time-varying spraying process parameters to each sub path and on the basis of the established multivariable spraying model, predicting distribution of an initial coating thickness; next, on the basis of a prediction result on distribution of the coating thickness, carrying out combined optimization on the time-varying process parameters to obtain the optimal process parameters on each section of sub path and finally, obtaining a multi-parameter time-varying spraying path of a surface to be sprayed. According to the method disclosed by the invention, various process parameters are used as variables; by the multivariable spraying model and a free-form surface coating thickness predicting method, the optimal process parameters on the sub paths of the discretized spraying path are obtained; dynamic optimization of the process parameters is implemented; the multi-parameter time-varying robot spraying method has the important effect of improving spraying operation efficiency, quality and safety of a robot.