The present invention discloses a coverage testing method, apparatus and system for a unit. The method comprises: inputting debugging data in a database into a state machine model, wherein the state machine model comprises states, paths and conditions, each state is used for representing a function of a to-be-debugged unit, each path represents a mode of switching from one state to the other state, and each condition represents a condition combination on each path; performing calculation on the debugging data according to the state machine model; performing state analysis on a calculation process, wherein the state analysis is used for determining whether the states, the paths and the conditions are all executed; and determining whether a coverage test is passed according to a determination result. According to the coverage testing method, apparatus and system, the technical problem of missing debugging caused by incomplete coverage during unit debugging is solved.