The invention provides a method for expanding functions with a set-top box script, which comprises the following steps of: carrying out login register on login performance functions in a hash table register login manner, classifying all login performance functions and allocating an independent internal memory space for each class with the purpose of memory; allocating a space in the internal memory space for storing the character strings of the login performance functions, the hash value of fixed length, the indicators of the login performance functions and other data; when a set-top box script program executes one login performance function, carrying hash operation on the character string of the login performance function called by the script program through a set-top box script analysis engine, comparing the obtained hash value with the hash value of fixed length in the space, and taking out the indicator corresponding to the login performance function for the call of the set-top box script analysis engine when the obtained hash value is equal to the hash value of fixed length in the space. According to the invention, the calling rate of the set-top box script program for required functions is increased, the running efficiency of the set-top box is improved and the convenience is brought to the user.