Model-based covert timing channels leak confidential information by modulating the inter-packet delays of consecutive packets.In order to evade detection, rather than directly making quantization-based embedding, the modulation and demodulation procedures based on the cumulative distribution function of legitimate traffic are frequently used in the encoding and decoding process of model-based covert timing channels.However, the detection-evading manner will also cause the additional symbol error due to the network delay jitters.This paper is concerned with symbol error rate analysis of model-based covert timing channel.The correctly recovering bound condition of confidential information symbols is given and proved.Moreover, a general expression of the symbol error rate for model-based covert timing channel is derived.The provided symbol error rote expressions offer a convenient way to evaluate model-based covert timing channel schemes.