Background: Married female caregivers face a higher risk of an informal care burden than other caregivers. No study has explored the effect of socioeconomic status (SES) on the intensity of informal care provided by married female caregivers in China. The purpose of this study is to empirically examine how the SES of married female caregivers affects the intensity of the informal care they provide for their parents/parents-in-law in China. Methods: The data for this study were drawn from 8 waves of the China Health and Nutrition Survey (CHNS). The respondents were married women whose parents/parents-in-law needed care and lived in the same city as them. SES was defined based on four indicators: education, economic status, employment status, and hukou (China’s household registration system). Informal caregivers were divided into three categories: non-caregivers (0 h/week), low-intensity caregivers (less than 10 h/week), and high-intensity caregivers (10 h/week and above). Multinomial logistic regression analysis was used to examine the relation between SES and the likelihood of a low- and high-intensity caregiving among married female caregivers, adjusting for age, family characteristics and survey wave. Results: Of the 2661 respondents, high-intensity and low-intensity caregivers accounted for 16.35 and 21.27%, respectively. The multinomial logistic regression results showed that the likelihood of being a high-intensity caregiver versus (vs. a non-caregiver) increased as the caregiver’s educational attainment increased (p < 0.05), and that high economic status was related to the likelihood of being a high-intensity caregiver, but this relationship was only significant at the 10% level. Urban females were 1.34 times more likely than their rural counterparts to provide low-intensity care vs. no care (p < 0.05) and were 1.33 times more likely to provide high-intensity care vs. no care (p < 0.05). Employed females were 1.25 times more likely than those unemployed females to provide low-intensity care vs. no care (p < 0.05). Conclusions: Differences in SES were found between high-intensity caregivers and low-intensity caregivers. Women with high educational attainment and urban hukou were more likely to provide high-intensity informal care, and women who were employed and had urban hukou were more likely to provide low-intensity care.