<p>The Cry proteins of Bacillus thuringiensis (Bt) produce parasporal crystal during sporulation which are toxic against insect larvae of lepidopteran, coleopteran and dipteran. In the present study, 10 native isolations of Bt strains were quantified from the Native Strains Bank of the Jorge Tadeo Lozano University, isolated from soil in the municipalities of Ráquira, Santa Sofía, Villa de Leyva and Sutamarchán, in Boyacá; and also in Susa, Cundinamarca. Crude extracts of total proteins from the 10 strains incubated in Luria-Bertani medium (LB) for 15 days at 37 °C were obtained. For quantification of total protein of the spore crystal mixture was used the Bradford method using a standard pattern a calibration curve with bovine serum albumin (BSA). After 5 minutes, the determination was realized in the spectrophotometer at a wavelength of 595 nm. The brighter blue were presented by the strains ZBUJTL35 and ZBUJTL39, with a concentration of 560.71 and 526.43 mg / ml, respectively. The Bradford method is a simple and fast technique to estimate the protein concentration. The strains will be used to determine the toxicity over Bemisiatabaci larvae.</p>