(1) Background: Plant growth regulators (PGRs) can accelerate growth or improve the quality and quantity of bean sprouts but are forbidden to use in bean sprout cultivation, as the sprouting process’s increased chemicals will disturb the PGRs analysis. This article aimed to increase the accuracy and level of sensitivity of the LC-MS/MS method for the simultaneous analysis of 10 PGRs after mixed solid phase extraction (SPE) purification. (2) Methods: An LC-MS/MS detection method for 10 kinds of PGRs was established based on ESI ionization in the positive ion mode for 6-furfurylaminopurine (6-KT), paclobutrazol (PBZ), indole-2-acetic acid (IAA), and indole-3-butyric acid (IBA) and in the negative ion mode for gibberellin A3 (GA3), 2,4-dichlorophenoxy acetic acid (2,4-D), 4-chlorophenoxyacetic acid (4-CPA), forchlorfenuron (FCF), thidiazuron (TDZ), and 6-benzyl adenine (6-BA). (3) Results: The 10 PGR compounds were detected within a concentration range of 1.0−50 ng/mL. The average recovery was 68.3−97.3% with relative standard deviations (RSD) of 4.6−15.2% (n = 6); the limit of detection (LOD) and limit of quantification (LOQ) were found to be 2 and 5 ng/g, respectively. PGRs were surveyed in 36 soybean sprouts and 33 mungbean sprouts; the results showed that 4-CPA and IAA were detected in 10 soybean sprouts and 10 mungbean sprouts, respectively. Five samples contained both 4-CPA and IAA. (4) Conclusions: The established method is simple, rapid, accurate, and highly sensitive for the detection of PGR residues in bean sprout products.