The combined effect of writing notations and response types on the spatial representation of fractions remains unclear. The present study explored this by employing a magnitude comparing task with irreducible and single-digit proper fractions as target stimuli as well as 1/2 ($$\frac{1}{2}$$
1
2
) as benchmarks for right-handed undergraduate students (64 males, 76 females; Mean age = 20.65 years, SD = 1.75, with normal or corrected-to-normal vision) in E-Prime 2.0 Professional Software platform. We found that: 1) for the horizontal response type, the horizontal writing notation of fractions did not produce a reliable SNARC effect or reversed SNARC effect; 2) for the same response type, the vertical writing notation of fractions elicited a SNARC effect; 3) for the vertical response type, both vertical and horizontal writing notations of fractions led to a reversed SNARC effect. These results indicated a combined effect of writing notations and response types on the spatial representation of fractions. Specifically, writing notations can affect the spatial representation of fractions under the condition of horizontal response types but not the vertical response types.