The successive years and average increments of the volumes of Larix olgensis and L. kaempferi were computed by Trunk Analysis, and the carbon content and carbon density of L. olgensis and L. kaempferi at their different age stages were measured with Germany Vario EL III element analyzer, aimed to approach the carbon storage maturity age of the two tree species. The results indicated that L. olgensis and L. kaempferi had a volume maturity age of 48.3 and 49.3 years, respectively, and the change trend of their carbon density was basically identical. The maximum carbon density was presented in the 30th year for L. olgensis and the 35th year for L. kaempfer. The successive years carbon storage of L. kaempferi was larger than that of L. olgensis, but the carbon storage maturity age was in adverse. The average carbon storage of L. kaempferi was also larger than that of L. olgensis. Through simulating the curve equations of successive years and average carbon storages, the carbon storage maturity age of L. olgensis and L. kaempferi were computed as 48.7 years and 47.7 years, respectively.