Huang (1984) proposes that null object is a variable controlled by a null topic, unlike null subject which is a real null pronoun. This paper tries to verify this proposal by investigating the distribution of null object in Cantonese. It is found that while Huang’s proposal is able to explain the majority part of the distribution of null object, it is unable to give an explanation to several cases related to resultativity and indirect object which disallow null object. A possible explanation is given to account for these cases, which is related to feature checking and a modified version of Huang’s Generalized Control Rule.