The Organic Rankine Cycle (ORC) has obvious advantages in the utilization of low-temperature heat source (80-300 degrees C). Based on specific heat source, this paper determines design conditions of radial-inflow turbine with six kinds of dry working fluids. This paper presents a new method for modeling of ORC based on radial-inflow turbine with the novel selection of initial design parameters. In the selection procedure of the initial design parameters, the properties of organic working fluids should be taken into consideration to control the increase of upsilon(2)/upsilon(1), which can lead to the large relative velocity ratio and the poor performance of the radial-inflow turbine. The study shows that the applicable selection area of initial design parameters differentiates from that recommended in the literature for organic working fluids. The lowest cycle ideal efficiency with R123 results in the minimums of the cycle thermal efficiency and the cycle net power, which reaches 8.33% and 67.24 kW, respectively. Although the relative internal efficiency of the radial-inflow turbine with R600a is in the middle level, the highest cycle thermal efficiency and cycle net power reach 9.17% and 74.59 kW, respectively. The results show that the ORC systems with R600 and R600a both have better cycle performance with smaller geometric dimensions and more excellent thermal matching with specific heat source.