To explore the relationship between physical activity level, muscle strength, working memory and cognitive function in older adults. A cross-sectional research design was employed to recruit 120 older adults individuals aged 70 and above. Participants were asked to complete the International Physical Activity Questionnaire-Short Form and the Montreal Cognitive Assessment Scale. Data on variables such as grip strength and performance on the N-back task were collected. Data analysis involved the use of independent samples t-tests, χ2 tests, linear regression analysis, Pearson correlation analysis, and one-way analysis of variance (ANOVA). The detection rate of cognitive dysfunction in older adults was 53.211%; 1-back correct rate had an explanatory power of 11.6% for the cognitive function scores of older adults (R2 = 0.116, p < 0.001); grip strength showed a significant positive correlation with 1-back correct rate (r = 0.417, p < 0.001), and was significantly correlated with the 0-back response time (r = -0.478), 1 -back response time (r = -0.441) were significantly negatively correlated (p < 0.001); physical activity level was significantly positively correlated with grip strength (r = 0.559, p < 0.001), and the difference in grip strength among older adults with different physical activity levels was statistically significant (F = 19.685, p < 0.001). Physical activity level, muscle strength, working memory, and cognitive function are closely related in older adults, and the relational pathway of physical activity → muscle strength → working memory → cognitive function may serve as a useful addition to promote the field of cognitive research in older adults. To identify and prevent cognitive decline in older adults, physical activity questionnaires, grip strength tests, and 1-back task tests can be extended to nursing homes and communities.