Penelitian ini menerapkan efektivitas sosialisasi K3 dan Kedisiplinan dalam praktek di SMK PGRI 2 Lahat. dalam tiga tahap yaitu pretest–sosialisai–posttest.penelitian ini, (1) mendeskripsikan K3 dalam pelaksaan praktek di program keahlian teknik kendaraan ringan siswa kelas X SMK PGRI 2 Lahat sebelum menerapkan efektivitas Sosialisasi K3, (2) mendeskripsikan K3 dalam pelaksaan praktek di program keahlian teknik kendaraan ringan siswa kelas X SMK PGRI 2 Lahat setelah menerapkan efektivitas Sosialisasi K3, (3) menjelaskan pengaruh efektivitas Sosialisasi K3 siswa kelas X SMK PGRI 2 Lahat Pretest dan posttest. Metode penelitian deskriptif analisis. Hasil sosialisasi penelitian ini, Pertama sebelum/pretest, sosialisasi K3 berada pada kualifikasi Hampir cukup dengan rata-rata nilai 45,6172. Kedua, setelah/posttest berada pada kualifikasi Baik Sekali (BS) rata-rata 90,4891. Ketiga, uji-t hipotesis alternatif (H1) diterima pada taraf signifikan 95% dan t-hitung(1,624 > 0,147). This study applies the effectiveness of K3 socialization and Discipline in practice at SMK PGRI 2 Lahat. three stages pretest–socialization–posttest. this study are, (1) to describe K3 in the implementation of practice in the light vehicle engineering expertise program of class X students of SMK PGRI 2 Lahat before implementing the effectiveness of K3 Socialization,(2) to describe K3 in the implementation practice in the vehicle engineering expertise program for students class X SMK PGRI 2 Lahat after implementing the effectiveness of K3 Socialization, (3) the effect of the effectiveness of K3 Socialization for students class X of SMK PGRI 2 Lahat Pretest and posttest. method descriptive analysis. Resultst this research socialization, First, before/pretest conducting K3 socialization are at the qualification Almost enough with an average score of 45.6172. Second, after/posttest is at an average 90.4891 Good (BS) qualifications. Third, the alternative hypothesis (H1) t-test is accepted at a significant level 95% and t-count (1.624 > 0.147).