This study examines the characteristics of similar and differentiated technologies in an industry to investigate firms’ technology accumulation patterns. Cosine similarity compares technology positions generated by the patent applications of two major Chinese firms in the robot cleaner industry. The analysis shows that as the number of patent applications increases, firms tend to accumulate standard technologies for the basic performance of products while accumulating differentiated technologies for specific products and functions. The combination of standard and specific technologies has the advantage of creating barriers to entry, but the disadvantage of being slower to adapt to changes in the business environment.