In the modern society filled with information and technology, the transmission of information among people has become fast and convenient. In the pursuit of speed and efficiency, we also begin to pay attention to the security of information in the sharing process. To secure the process in sharing information, cryptography has become a hot topic of research. Traditional cryptography requires complex mathematical operations to restore secret information. In 1994, Naor & Shamir proposed a (k,n)-threshold visual secret sharing scheme, which can share a secret image among n individuals. In the scheme, each individual will receive a share image which reveals no secret. The secret information can be restored and identified by human eyes only when k or more share images are superimposed. In their work, Naor & Shamir only showed some examples of the (k,n) scheme for specific k and n. In 2014, Guan et al. devised a systematic method for the (3, n)-threshold visual secret sharing scheme, which can allow sharing among any number of individuals with a visual restoration threshold of k=3. That is, each share image will reveal no secret. Nor will any two share images show anything when superimposed together. The secret information will reveal only when k=3 or more share images are superimposed. In this work, we will continue to find a systematic method for the (4, n)-threshold visual secret sharing scheme. We will empirically validate the method by examples.