Recently, Mao, Zhang, Wu et al. constructed two key exchange (KE) protocols based on tensor ergodic problem (TEP). Al-though they conjectured that these construc-tions can potentially resist quantum computing attack, they did not provide a rigorous security proof for their KE protocols. In this paper, applying the properties of ergodic matrix, we first present a polynomial time algorithm to solve the TEP problem using O(n6) arithmetic operations in the finite field, where n is the security parameter. Then, applying this poly-nomial time algorithm, we generate a common shared key for two TEP-based KE construc-tions, respectively. In addition, we also pro-vide a polynomial time algorithm with O(n6) arithmetic operations that directly recovers the plaintext from a ciphertext for the KE-based encryption scheme. Thus, the TEP-based KE protocols and their corresponding encryption schemes are insecure.