The invention relates to a method for establishing a cracking product component soft measurement model for cracking naphtha to prepare ethylene. The method comprises: through a one-to-one correspondence relationship of the observation variables related to the prediction variables in a historical period, determining a plurality of soft measurement models, verifying the soft measurement model through verification data; eliminating a soft measurement model with a large error; testing by using off-line data of a historical period; obtaining a final optimal soft measurement model from the pluralityof soft measurement models. Prediction of some variables which cannot be accurately measured in real time or are high in measurement cost is realized. The real-time variable measurement cost is reduced, the soft measurement model capable of describing the target process is established based on the historical data of the cracking process before the parameter variables are predicted in real time, and the accuracy degree of the model is directly related to the precision of the prediction result of each component of the cracking product.