The stable carbon isotope ratios (δ¹³C) of the six herbaceous plants (including 3 C3 species and 3 C4 species) and their responses to temperature change were explored in artificial controlled environments at day/night temperatures ranging from 20/12 to 36/28℃. The correlations between plants δ¹³C values and the growth and photosynthetic indexes, such as specific leaf area (SLA), the ratio of intercellular CO₂ concentration (c_i) to environmental CO₂ concentration (c_a), and carbon assimilation rate (net photosynthetic rate P_n/c_i) were also analyzed in order to investigate the temperature effects on carbon-isotope ratio of C3 and C4 herbs. The results showed that, the δ¹³C values of C3 and C4 plants ranged between -28.3 ‰ to -32.1 ‰, and between -14.4 ‰ to -17.6 ‰, respectively. In the three C3 species, rape (Brassica campestris) had the most concentrated distribution of δ¹³C values, with an range of -31.1 ‰ to -32.1 ‰; and the δ¹³C value distribution for millet (Setaria italica) was the narrowest in the three C4 plants. In the experimental temperature range, the mean δ¹³C values of three C3 plants significantly decreased with increasing temperature, while a parabolic relationship showing an increase first and then decrease existed between the average δ¹³C values of three C4 plants and temperature, however, the linear regression result was not significant (P >0.05). The δ¹³C values of individual species responded differently to temperature. The δ¹³C values in eggplant (Solanum melongena) and sorghum (Sorghum bicolor) negatively correlated with temperature, and the δ¹³C values of other four species all showed a quadratic parabola relationship with temperature, which may be associated with different plant species that have different optimum photosynthesis temperature and carbon isotope fractionation capacities to temperature.